Upgrade my oVirt yesterday from 3.3.4 to 3.4.0..
For my surprise, the node of 3.3 not running in 3.4 (Cluster version)
Ok... move to maintenance and upgrade :P
But... Maintenance not is running for 10+ minutes.. (No live migration progress)
I restart the ovirt-engine and live migration running and node is maintenance mode.. (nice!!)
But.............. (yes, again)... remove the node from ovirt engine not is possible, this message error  in engine.log: