megasas: clean up and fix request completion/cancellation

megasas: clean up and fix request completion/cancellation

megasas_command_cancel is a callback; it should report the abort in
the frame, not try another abort!  Compare for instance with
mptsas_request_cancelled.

So extract the common bits for request completion in a new function
megasas_complete_command, call it from both the .complete and .cancel
callbacks, and remove duplicate pieces from the DCMD path.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20161110152751.4267-2-pbonzini@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>