engine: Fix issue with thread naming

Patch http://gerrit.ovirt.org/#/c/19744/ appended org.ovirt.thread
to the thread name. However, this happened again and again, with
no limit. This patch fixes it.

Change-Id: I4094f70859802a11cbd9150461e5af1ae583a17a
Signed-off-by: lzelkha@redhat.com <lzelkha@redhat.com>