If .META. offline between OPENING and OPENED, then wrong server location in .META. is possible

This is a good one. It happened to me testing OOME in split logging.

• Balancer moves region to new location, regionservrer X.
• New location regionserver X successfully opens the region and then goes to update .META.
• At this point, the server carrying .META. crashes.
• Regionserver X is stuck waiting on .META. to come back online. It takes so long master times out the region-in-transition
• Master assigns the region elsewhere to regionserver Y
• It opens successfully on regionserver Y and then it also parks waiting on .META. coming online
• .META. comes online
• The two servers X and Y race to update .META.

I saw case where server X edit went in after server Ys edit which means that lookups in .META. get the wrong server. HBCK can detect this situation.

RegionServer X when it wakes up coreeclty notices that its lost control of the region but the damage is done – where damage is .META. edit.

Chatting with Jon, he suggested that regionserver X should 'rollback' the .META. edit – do explicit delete of what it added. This would work I think but chatting more, I'll make a fix that keeps updating the zookeeper OPENING state while edit goes on in a separate thread. Our continuous setting of OPENING will make it so region-in-transition does not timeout.