use a safe iterator when deleting clients during comp shutdown
use a safe iterator when deleting clients during comp shutdown

it's conceivable that, were there a bug in client refcounting,
this could become an infinite loop and prevent shutdown/restart.
since, at this point, we don't really care about deleting anything,
ensure that the loop will end

tasn/enlightenment,tizenorg/platform.upstream.enlightenment,rvandegrift/e,FlorentRevest/Enlightenment,tasn/enlightenment,tizenorg/platform.upstream.enlightenment,rvandegrift/e,FlorentRevest/Enlightenment,tasn/enlightenment,rvandegrift/e,FlorentRevest/Enlightenment,tizenorg/platform.upstream.enlightenment