Description of problem:

In case gluster fencing policy check fails, _getVolumeStatus returns an empty dict[1]. Then, can_fence_host iterates through the returned empty dict with the method .get("bricks"), which is None. This throws an ugly exception[3] in the logs. If it happens frequently, it can spam significantly.

In addition, in the related code there are two typos ("realted" instead of "related") here[4] and here[5].

[1] https://github.com/oVirt/vdsm/blob/master/lib/vdsm/gluster/fence.py#L112
[2] https://github.com/oVirt/vdsm/blob/master/lib/vdsm/gluster/fence.py#L39
[3]
2019-02-28 14:43:21,324+0000 WARN  (jsonrpc/1) [Gluster] Failed to check
gluster realted fencing policies: Command execution failed
error: Error : Request timed out
return code: 1 (fence:109)
2019-02-28 14:43:21,324+0000 ERROR (jsonrpc/1) [DynamicBridge] TypeError
raised by dispatched function (Bridge:199)
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/vdsm/rpc/Bridge.py", line 193,
in _dynamicMethod
    result = fn(*methodArgs)
  File "/usr/lib/python2.7/site-packages/vdsm/API.py", line 1265, in
fenceNode
    if action != 'status' and not should_fence(policy):
  File "/usr/lib/python2.7/site-packages/vdsm/API.py", line 1193, in
should_fence
    result = check_gluster_fencing_policies(policy)
  File "/usr/lib/python2.7/site-packages/vdsm/API.py", line 1250, in
check_gluster_fencing_policies
    skipFencingIfGlusterQuorumNotMet)
  File "/usr/lib/python2.7/site-packages/vdsm/gluster/fence.py", line
37, in can_fence_host
    for brick in volStatus.get('bricks'):
TypeError: 'NoneType' object is not iterable
[4] https://github.com/oVirt/vdsm/blob/master/lib/vdsm/gluster/fence.py#L101
[5] https://github.com/oVirt/vdsm/blob/master/lib/vdsm/gluster/fence.py#L110