Fix MongoDB DocumentSizeUpdater tests

java.lang.AssertionError
	at org.junit.Assert.fail(Assert.java:86)
	at org.junit.Assert.assertTrue(Assert.java:41)
	at org.junit.Assert.assertNotNull(Assert.java:621)
	at org.junit.Assert.assertNotNull(Assert.java:631)
	at org.nuxeo.ecm.quota.count.TestDocumentsSizeUpdater.assertQuota(TestDocumentsSizeUpdater.java:1869)
	at org.nuxeo.ecm.quota.count.TestDocumentsSizeUpdater$40.run(TestDocumentsSizeUpdater.java:963)
	at org.nuxeo.ecm.quota.count.IsolatedSessionRunner.run(IsolatedSessionRunner.java:53)
	at org.nuxeo.ecm.quota.count.TestDocumentsSizeUpdater.testComputeInitialStatistics(TestDocumentsSizeUpdater.java:956)

Standard Output
Nuxeo-Work-quota-1:test:quotaInitialStatistics:documentsSizeUpdater 05:25:29,822 ERROR [AbstractWork] Exception during work: org.nuxeo.ecm.quota.QuotaStatsInitialWork@6c1db6a4[updaterName=documentsSizeUpdater,repositoryName=test]
com.mongodb.WriteConcernException: Write failed with error code 16837 and error message 'Cannot apply $inc to a value of non-numeric type. {_id: ObjectId('5722f0334cedfd26dc930361')} has the field 'dss:sizeTrash' of non-numeric type NULL'
	at com.mongodb.operation.BaseWriteOperation.convertBulkWriteException(BaseWriteOperation.java:239)
	at com.mongodb.operation.BaseWriteOperation.access$300(BaseWriteOperation.java:60)
	at com.mongodb.operation.BaseWriteOperation$1.call(BaseWriteOperation.java:146)
	at com.mongodb.operation.BaseWriteOperation$1.call(BaseWriteOperation.java:133)
	at com.mongodb.operation.OperationHelper.withConnectionSource(OperationHelper.java:230)
	at com.mongodb.operation.OperationHelper.withConnection(OperationHelper.java:221)
	at com.mongodb.operation.BaseWriteOperation.execute(BaseWriteOperation.java:133)
	at com.mongodb.operation.BaseWriteOperation.execute(BaseWriteOperation.java:60)
	at com.mongodb.Mongo.execute(Mongo.java:781)
	at com.mongodb.Mongo$2.execute(Mongo.java:764)
	at com.mongodb.DBCollection.executeWriteOperation(DBCollection.java:333)
	at com.mongodb.DBCollection.updateImpl(DBCollection.java:495)
	at com.mongodb.DBCollection.update(DBCollection.java:455)
	at com.mongodb.DBCollection.update(DBCollection.java:432)
	at com.mongodb.DBCollection.update(DBCollection.java:522)
	at com.mongodb.DBCollection.update(DBCollection.java:537)
	at org.nuxeo.ecm.core.storage.mongodb.MongoDBRepository.updateState(MongoDBRepository.java:548)
	at org.nuxeo.ecm.core.storage.dbs.DBSTransactionState.save(DBSTransactionState.java:569)
	at org.nuxeo.ecm.core.storage.dbs.DBSSession.save(DBSSession.java:175)
	at sun.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.nuxeo.ecm.core.storage.dbs.DBSRepositoryBase$DBSSessionInvoker.invoke(DBSRepositoryBase.java:429)
	at com.sun.proxy.$Proxy27.save(Unknown Source)
	at org.nuxeo.ecm.core.api.AbstractSession.save(AbstractSession.java:1415)
	at org.nuxeo.ecm.core.api.UnrestrictedSessionRunner.runUnrestricted(UnrestrictedSessionRunner.java:151)
	at org.nuxeo.ecm.quota.QuotaStatsInitialWork.work(QuotaStatsInitialWork.java:74)
	at org.nuxeo.ecm.core.work.AbstractWork.runWorkWithTransaction(AbstractWork.java:416)
	at org.nuxeo.ecm.core.work.AbstractWork.runWorkWithTransactionAndCheckExceptions(AbstractWork.java:377)
	at org.nuxeo.ecm.core.work.AbstractWork.run(AbstractWork.java:338)
	at org.nuxeo.ecm.core.work.WorkHolder.run(WorkHolder.java:57)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
	at java.lang.Thread.run(Thread.java:745)

java.lang.AssertionError: inner: expected:<380> but was:<760>
	at org.junit.Assert.fail(Assert.java:88)
	at org.junit.Assert.failNotEquals(Assert.java:743)
	at org.junit.Assert.assertEquals(Assert.java:118)
	at org.junit.Assert.assertEquals(Assert.java:555)
	at org.nuxeo.ecm.quota.count.TestDocumentsSizeUpdater.assertQuota(TestDocumentsSizeUpdater.java:1870)
	at org.nuxeo.ecm.quota.count.TestDocumentsSizeUpdater$66.run(TestDocumentsSizeUpdater.java:1456)
	at org.nuxeo.ecm.quota.count.IsolatedSessionRunner.run(IsolatedSessionRunner.java:53)
	at org.nuxeo.ecm.quota.count.TestDocumentsSizeUpdater.testQuotaOnRevertVersion(TestDocumentsSizeUpdater.java:1445)