When a block{pull, copy, commit} is aborted via keyboard interrupt,
the job is properly canceled followed by proper error message.
However, when the job receives an abort from another client connected
to the same domain, the error message incorrectly indicates that
a blockjob has been finished successfully, though the abort request
took effect. This patch introduces a new blockjob abort handler, which
is registered when the client calls block{copy,commit,pull} routine,
providing its caller the status of the finished blockjob.
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1135442
8312d44d72