The invocation does not require a channel to
 support external SCCs invocations.

 Creating specific unit-tests for retrieving the proper
 txContext from the handler.

 Any SCC to SCC unit tests are kept in the history of this
 patch and are reverted from the final patch. To review
 these tests, please check gerrit for the history.

Change-Id: I6d9b2da9c8b7c447244a180b4705a386b997a7fa
Signed-off-by: Baha Shaaban <baha.shaaban@securekey.com>