SyncReplTest#testMixingSyncAndAsyncOnSameTransport() looks to be broken

Please see https://github.com/infinispan/infinispan/blob/master/core/src/test/java/org/infinispan/replication/SyncReplTest.java. When we switch lines 205 and 219 it pass with no problem. I expect that this shouldn't pass.

The problem is - how we can properly test whether replication call was SYNC or ASYNC.

Assigning to Tristan (or Mircea? familiar with mockito..) according to Manik's answer.