build failing all MongoDBArtifactStoreTests tests

Travis is currently broken. The most recent build https://app.travis-ci.com/github/apache/openwhisk/builds/241701957.

```
> ./tools/build/citool monitor -r 241701957.2
org.apache.openwhisk.core.database.mongodb.MongoDBAttachmentStoreTests > MongoDBArtifactStore attachments should generate different attachment name on update FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBAttachmentStoreTests > MongoDBArtifactStore attachments should fail on reading with old non inlined attachment FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBAttachmentStoreTests > MongoDBArtifactStore attachments should work on reading with old inlined attachment FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBAttachmentStoreTests > MongoDBArtifactStore attachments should put and read large attachment FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBAttachmentStoreTests > MongoDBArtifactStore attachments should inline small attachments FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBAttachmentStoreTests > MongoDBArtifactStore attachments should throw NoDocumentException for non existing attachment FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBAttachmentStoreTests > MongoDBArtifactStore attachments should delete attachment on document delete FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore query should find single entity FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore query should not have doc with includeDocs = false FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore query should find all entities FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore query should exclude deleted entities FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore query should return result in sorted order FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore query should support skipping results FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore query should support limiting results FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore query should support including complete docs FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore query should throw exception for negative limits and skip FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore count should should match all created activations FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore count should count with skip FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore count should throw exception for negative skip FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore put should put document and get a revision 1 FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore put should put and update document FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore put should put delete and then recreate document with same id with different rev FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore put should throw DocumentConflictException when updated with old revision FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore put should throw DocumentConflictException if document with same id is inserted twice FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore put should work if same document was deleted earlier FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore delete should deletes existing document FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore delete should throws IllegalArgumentException when deleting without revision FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore delete should throws NoDocumentException when document does not exist FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore delete should throws DocumentConflictException when revision does not match FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore get should get existing entity matching id and rev FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore get should get existing entity matching id only FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore get should get entity with timestamp FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore get should throws DocumentRevisionMismatchException when document revision does not match FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore get should throws NoDocumentException when document does not exist FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore get should not get a deleted document FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore query subjects should find subject by namespace FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore query subjects should not get blocked subject FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore query subjects should not find subject when authKey matches partially FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore query subjects should should throw NoDocumentException for non existing namespaces FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore query subjects should should throw NoDocumentException for non existing authKeys FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore query subjects should find subject having multiple namespaces FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore query subjects should find subject by namespace with limits FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore query subjects should find blacklisted namespaces FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore query public packages should only list published entities FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore query public packages should list packages between given times FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore query public packages should list activations between given times FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore attachments should generate different attachment name on update FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore attachments should fail on reading with old non inlined attachment FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore attachments should work on reading with old inlined attachment FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore attachments should put and read large attachment FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore attachments should inline small attachments FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore attachments should throw NoDocumentException for non existing attachment FAILED
org.apache.openwhisk.core.database.mongodb.MongoDBArtifactStoreTests > MongoDBArtifactStore attachments should delete attachment on document delete FAILED
```