Fixes CC-1146: Remove unavailable host
Fixes CC-1146: Remove unavailable host

If zookeeper can't contact the no-longer-available host, don't fail--
keep going and clean up the rest of the host's remnants.  (Admin will
have to manually recover zookeeper to clear out the stuck entries.)

control-center/serviced,control-center/serviced,control-center/serviced,control-center/serviced,control-center/serviced,control-center/serviced,control-center/serviced,control-center/serviced