Data-Generator fails for AVRO on "complexWebsite" pattern

Fix avro format on data generator for "complexWebsite"

Via Mahesh on Slack:

> Hi Alex, This works for csv but not avro.. I checked code and see it supports 2 formats csv and avro
> [1:53 PM] myeole-a01:bin myeole$ ./pinot-admin.sh GenerateData -numFiles 1 -numRecords 354780 -format avro -schemaFile /scratch/myeole/incubator-pinot/pinot-tools/src/main/resources/generator/complexWebsite_schema.json -schemaAnnotationFile /scratch/myeole/incubator-pinot/pinot-tools/src/main/resources/generator/complexWebsite_generator.json -outDir ./myTestData1201sd
> Using Java version: 1.8
> Executing command: GenerateData -numRecords 354780 -numFiles 1 -schemaFile /scratch/myeole/incubator-pinot/pinot-tools/src/main/resources/generator/complexWebsite_schema.json -outDir ./myTestData1201sd -schemaAnnotationFile /scratch/myeole/incubator-pinot/pinot-tools/src/main/resources/generator/complexWebsite_generator.json
> Exception caught:
> java.lang.RuntimeException: Invalid Field type.
> at org.apache.pinot.tools.data.generator.DataGenerator.buildSpec(DataGenerator.java:154) ~[pinot-all-0.7.0-SNAPSHOT-jar-with-dependencies.jar:0.7.0-SNAPSHOT-0565f86ff9d8fcb1345f3e393d48d1cadd1320a5]
>