dm mpath: fix stalls when handling invalid ioctls

commit a1989b330093578ea5470bea0a00f940c444c466 upstream.

An invalid ioctl will never be valid, irrespective of whether multipath
has active paths or not.  So for invalid ioctls we do not have to wait
for multipath to activate any paths, but can rather return an error
code immediately.  This fix resolves numerous instances of:

 udevd[]: worker [] unexpectedly returned with status 0x0100

that have been seen during testing.

Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>