Description of problem:
After removing a fibrechannel storage domain, hosts went non-responsive because hypervisor was attempting to resize the missing LUN long after the removal.

Version-Release number of selected component (if applicable):
vdsm-4.20.35-1.el7ev.x86_64
rhvm-4.2.6.4-0.1.el7ev.noarch

How reproducible:
unknown

Steps to Reproduce:
1. Place fibrechannel storage domain into maintenance and remove it
2. After removal is complete, un-map LUNs from storage device

Actual results:
Hosts go non-operational and non-responsive with the following traceback:
~~~
2018-11-30 13:31:51,635-0600 INFO  (jsonrpc/0) [storage.Multipath] Resizing map '2621eba8c55434a026c9ce900941db8bd' (map_size=1099511627776, slave_size=0) (multipath:119)
2018-11-30 13:31:51,671-0600 ERROR (jsonrpc/0) [storage.Multipath] Could not resize device 2621eba8c55434a026c9ce900941db8bd (multipath:98)
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/vdsm/storage/multipath.py", line 96, in resize_devices
    _resize_if_needed(guid)
  File "/usr/lib/python2.7/site-packages/vdsm/storage/multipath.py", line 120, in _resize_if_needed
    supervdsm.getProxy().resizeMap(name)
  File "/usr/lib/python2.7/site-packages/vdsm/common/supervdsm.py", line 55, in __call__
    return callMethod()
  File "/usr/lib/python2.7/site-packages/vdsm/common/supervdsm.py", line 53, in <lambda>
    **kwargs)
  File "<string>", line 2, in resizeMap
  File "/usr/lib64/python2.7/multiprocessing/managers.py", line 773, in _callmethod
    raise convert_to_error(kind, result)
Error: Resizing map 'dm-10' failed: out='fail\n' err=''
2018-11-30 13:31:52,883-0600 INFO  (itmap/0) [IOProcessClient] (/cdnfs01.capella.edu:_nfs__cdnafs__rhv__export) Starting client (__init__:308)
~~~

Expected results:
No interruption on hypervisors

Additional info: