Avoid duplicating exception message
Avoid duplicating exception message

Now that we have exception chaining working nicely we
do not need to duplicate the original exceptions message
in followup exceptions (as the chain will by its very nature
have this same information/message); so let's stop duplicating
it.

Change-Id: I9b947c0d8c1df894de346835f92c12e8773349c4

pombredanne/taskflow-1,jimbobhickville/taskflow,openstack/taskflow,openstack/taskflow,jimbobhickville/taskflow,pombredanne/taskflow-1,junneyang/taskflow,junneyang/taskflow