The set tablet availability operation acquires a write lock over an infinite range. The range could be narrowed based on the range of tablets it is operating on. This is slightly tricky because that operation uses a key range instead of a row range. Also that operation may be able to switch to a read lock instead of a write lock, its not doing anything destructive like deleting or adding tablets or making significant zookeeper changes.

This is follow on work for after #5786 is merged