JsonSerializationException on breaking changes pass

The "Breaking Changes" check for [this PR](https://github.com/Azure/azure-rest-api-specs/pull/4047) is failing with the following somewhat cryptic error:
```
Executing : autorest --input-file=specification/deploymentmanager/resource-manager/Microsoft.DeploymentManager/preview/2018-09-01-preview/deploymentmanager.json --output-artifact=swagger-document.json --output-file=deploymentmanager --output-folder=/tmp/resolved/specification/deploymentmanager/resource-manager/Microsoft.DeploymentManager/preview/2018-09-01-preview
Resolved map for the new specifications:
{ 'specification/deploymentmanager/resource-manager/Microsoft.DeploymentManager/preview/2018-09-01-preview/deploymentmanager.json': '/tmp/resolved/specification/deploymentmanager/resource-manager/Microsoft.DeploymentManager/preview/2018-09-01-preview/deploymentmanager.json' }

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Old Spec: "specification/deploymentmanager/resource-manager/Microsoft.DeploymentManager/preview/2018-09-01-preview/deploymentmanager.json"
New Spec: "/tmp/resolved/specification/deploymentmanager/resource-manager/Microsoft.DeploymentManager/preview/2018-09-01-preview/deploymentmanager.json"
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

{ Error: Command failed: dotnet /home/travis/build/Azure/azure-rest-api-specs/node_modules/oad/lib/dlls/OpenApiDiff.dll -o /tmp/old.json -n /tmp/new.json -JsonValidationMessages

Unhandled Exception: Newtonsoft.Json.JsonSerializationException: Cannot deserialize the current JSON array (e.g. [1,2,3]) into type 'AutoRest.Swagger.Model.Operation' because the type requires a JSON object (e.g. {"name":"value"}) to deserialize correctly.
To fix this error either change the JSON to a JSON object (e.g. {"name":"value"}) or change the deserialized type to an array or a type that implements a collection interface (e.g. ICollection, IList) like List that can be deserialized from a JSON array. JsonArrayAttribute can also be added to the type to force it to deserialize from a JSON array.
Path 'paths['/subscriptions/{subscriptionId}/resourceGroups/{resourceGroupName}/providers/Microsoft.DeploymentManager/serviceTopologies/{serviceTopologyName}'].parameters', line 21, position 21.
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.EnsureArrayContract(JsonReader reader, Type objectType, JsonContract contract)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateList(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, Object existingValue, String id)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.PopulateDictionary(IDictionary dictionary, JsonReader reader, JsonDictionaryContract contract, JsonProperty containerProperty, String id)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateObject(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerMember, Object existingValue)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.PopulateDictionary(IDictionary dictionary, JsonReader reader, JsonDictionaryContract contract, JsonProperty containerProperty, String id)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateObject(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerMember, Object existingValue)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.SetPropertyValue(JsonProperty property, JsonConverter propertyConverter, JsonContainerContract containerContract, JsonProperty containerProperty, JsonReader reader, Object target)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.PopulateObject(Object newObject, JsonReader reader, JsonObjectContract contract, JsonProperty member, String id)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.CreateObject(JsonReader reader, Type objectType, JsonContract contract, JsonProperty member, JsonContainerContract containerContract, JsonProperty containerMember, Object existingValue)
at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType, Boolean checkAdditionalContent)
at Newtonsoft.Json.JsonSerializer.DeserializeInternal(JsonReader reader, Type objectType)
at Newtonsoft.Json.JsonConvert.DeserializeObject(String value, Type type, JsonSerializerSettings settings)
at Newtonsoft.Json.JsonConvert.DeserializeObject[T](String value, JsonSerializerSettings settings)
at AutoRest.Swagger.SwaggerModeler.Compare(String swaggerPrevious, String swaggerNew, Settings settings) in /home/travis/build/Azure/openapi-diff/openapi-diff/src/modeler/AutoRest.Swagger/SwaggerModeler.cs:line 18
at OpenApiDiff.Program.Main(String[] args) in /home/travis/build/Azure/openapi-diff/openapi-diff/src/core/OpenApiDiff/Program.cs:line 33
Aborted (core dumped)

at ChildProcess.exithandler (child_process.js:276:12)
at emitTwo (events.js:126:13)
at ChildProcess.emit (events.js:214:7)
at maybeClose (internal/child_process.js:915:16)
at Socket.stream.socket.on (internal/child_process.js:336:11)
at emitOne (events.js:116:13)
at Socket.emit (events.js:211:7)
at Pipe._handle.close [as _onclose] (net.js:561:12)
killed: false,
code: 134,
signal: null,
cmd: 'dotnet /home/travis/build/Azure/azure-rest-api-specs/node_modules/oad/lib/dlls/OpenApiDiff.dll -o /tmp/old.json -n /tmp/new.json -JsonValidationMessages' }
```

There was a breaking change in the PR (one property was renamed) so I would expect it to fail - but that was the only change (apart from descriptions) so I'm not sure what caused this error.

Any thoughts?

Thanks!

Riproduci il comando che fallisce sulla specifica deploymentmanager e ispeziona il valore di parameters nel percorso indicato. Inizia da AutoRest.Swagger/SwaggerModeler.cs riga 18 e OpenApiDiff/Program.cs riga 33, quindi verifica che il controllo delle breaking changes gestisca la specifica e segnali la proprietà rinominata invece di interrompersi.

Scritto dal modello di indicizzazione a partire dal testo della issue.