gluster: Show the wait icon if task status UNKNOWN

Modified to display the question mark icon if the task
status of rebalance / remove bricks is UNKNOWN.
This is required if task is in progress and because of storage nodes
down the status is returned as UNKNOWN.

Change-Id: I525231ea4127b247350fcb1f282a8592ae08a895
Bug-Url: https://bugzilla.redhat.com/1035601
Signed-off-by: Shubhendu Tripathi <shtripat@redhat.com>