Found the problem..
I did tcpdump and found that some DNS requests didn't get responeses.
One of upstream DNS servers didn't have TCP enabled for DNS requests so requests that
were sent to that server were unanswered, thats why I had Engine restarts at random
times.
Since I don't control upstream DNS servers (my ovirt DNS server is Gateway that just
resends reqests to upstream) .
I am thinking that maybe ping would be better in my case for liveness check..