IracTombstoneCleanupTest fails randomly

Tests in IracTombstoneCleanupTest are not properly isolated from each other and, if a command from a previous test is delivered in the next test, it causes it to fail.

Failures:

[ERROR] Failures: 
[ERROR]   IracTombstoneCleanupTest.testNonOwnerRoundCleanupLocally:196
[ERROR]   IracTombstoneCleanupTest.testPrimaryOwnerRoundCleanupsBackup:101 expected:<1> but was:<2>
[ERROR]   IracTombstoneCleanupTest.testStateTransfer:224 expected:<0> but was:<2>
[INFO] 
[ERROR] Tests run: 4, Failures: 3, Errors: 0, Skipped: 0

Trace logs shows IracTombstoneCleanupTest.testBackupOwnerRoundCleanupDoNotCleanupPrimary is sending a IracTombstonePrimaryCheckCommand. This command should be received by the primary owner and it should be a no-op operation. Since the command is sent asynchronously, the test completes without ensuring the command is really handled.

We need to decorate DefaultIracTombstoneManager to make sure the command is handled before moving to the next test method.