https://bugzilla.redhat.com/show_bug.cgi?id=1536461

This reverts commit aeda1b8c.

Problem is that we need mon->lastError to be set because it's
used all over the place. Also, there's nothing wrong with
reporting error if one occurred. I mean, if there's a thread
executing an API and which currently is talking on monitor it
definitely wants the error reported.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>