Description of problem: GlusterFS starts the rebalance task even when few bricks are down in a distributed volume. But when you see the rebalance status, it fails in all the nodes. This also happens for replicate/striped volumes when a complete set of bricks in a replica group is down. Similar can be seen in 'Remove Brick Start' asynchronous task.

How reproducible:
   Start rebalance on a distributed volume in which few brick processes are down.

Steps to Reproduce:
1. Create a volume with 3 bricks 
2. Kill one of the brick process
3. Start volume rebalance on the volume created

Actual results:

   Rebalance task starts with a task ID and if you check for the task/rebalance status, it will be failed from all the nodes.

Expected results:

   'Rebalance Start' should report an error without starting the rebalance task.

Additional info:

  Same thing reproducible in a replicated volume with all bricks of a replica group down. Similar behaviour observed in remove brick start (brick migration) use case.