mock out metrics in tests

services/track-changes/test/unit/coffee/DocArchive/MongoAWS.coffee

@@ -26,6 +26,7 @@ describe "MongoAWS", ->
 			"./mongojs" : { db: @db = {}, ObjectId: ObjectId }
 			"JSONStream": @JSONStream = {}
 			"readline-stream": @readline = sinon.stub()
+			'./Metrics': {inc: ()->}
 
 		@project_id = ObjectId().toString()
 		@doc_id = ObjectId().toString()

services/track-changes/test/unit/coffee/PackManager/PackManagerTests.coffee

@@ -20,6 +20,7 @@ describe "PackManager", ->
 			"./LockManager" : {}
 			"./MongoAWS": {}
 			"logger-sharelatex": { log: sinon.stub(), error: sinon.stub() }
+			'./Metrics': {inc: ()->}
 		@callback = sinon.stub()
 		@doc_id = ObjectId().toString()
 		@project_id = ObjectId().toString()