Remove dependency on BusAttachment when generating Messages.

This is to facilitate generating Messages for unit tests.

Change-Id: If9c6e9371f8a99a3e601f871c7451a2a28b7a6ed
Signed-off-by: Todd Malsbary <tmalsbar@qce.qualcomm.com>
ASACORE-1323: Assert that return value of ErrorMsg and ReplyMsg are OK

instead of pushing garbage through the system.

Change-Id: Ic6dc160635d54917077cb4081b1810ccb19054f6
Signed-off-by: Todd Malsbary <tmalsbar@qce.qualcomm.com>