Catch libvirt timeout and return an error on setVmTicket

Return an errCode instead of an exception libvirt timeout in setVmTicket
verb and setting the 'message' to be the exception string representation
so upper layers would have more info about what went wrong.

Change-Id: Ibb48a1baff1e059f48f71f600f4bf5d9f40a7d11
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=878064
Signed-off-by: Roy Golan <rgolan@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/10285
Reviewed-by: Dan Kenigsberg <danken@redhat.com>