Mixed_sync_async_in_query_cache is flaky

[smitpatel]

Microsoft.EntityFrameworkCore.Query.AsyncSimpleQuerySqlServerTest.Mixed_sync_async_in_query_cache
  No source available
   Duration: 6 ms

  Message: 
    Microsoft.Data.SqlClient.SqlException : The incoming tabular data stream (TDS) protocol stream is incorrect. The MARS TDS header contained errors.
  Stack Trace: 
    at SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
    at TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
    at TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)
    at SqlDataReader.TryConsumeMetaData()
    at SqlDataReader.get_MetaData()
    at SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString, Boolean isInternal, Boolean forDescribeParameterEncryption, Boolean shouldCacheForAlwaysEncrypted)
    at SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean isAsync, Int32 timeout, Task& task, Boolean asyncWrite, Boolean inRetry, SqlDataReader ds, Boolean describeParameterEncryptionRequest)
    at SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, TaskCompletionSource`1 completion, Int32 timeout, Task& task, Boolean& usedCache, Boolean asyncWrite, Boolean inRetry, String method)
    at SqlCommand.ExecuteReader(CommandBehavior behavior)
    at RelationalCommand.ExecuteReader(RelationalCommandParameterObject parameterObject) in RelationalCommand.cs line: 363
    at Enumerator.MoveNext() in QueryingEnumerable.cs line: 94
    at List`1.ctor(IEnumerable`1 collection)
    at Enumerable.ToList[TSource](IEnumerable`1 source)
    at AsyncSimpleQueryTestBase`1.Mixed_sync_async_in_query_cache() in AsyncSimpleQueryTestBase.cs line: 261
    at --- End of stack trace from previous location where exception was thrown ---

[smitpatel]

Related dotnet/SqlClient#85

[ajcvickers]

@divega to follow up with SqlClient.

[divega]

@smitpatel does this happen on specific OS platforms?

[divega]

I talked to @smitpatel offline and this happens on Windows, which I think it is consistent with dotnet/SqlClient#85.

[ajcvickers]

Triage: On the backlog as blocked by dotnet/SqlClient#85 so that we can re-enable the test once that issue is fixed.

[ajcvickers]

Test was reenabled as part of #27050.