Monitor/msg: Don't print error message if mdmon doesn't run

Monitor/msg: Don't print error message if mdmon doesn't run

Commit 4515fb28a53a ("Add detail information when can not connect
monitor") was added to warn about failed connection to monitor in
WaitClean function (see link below).

Mdmon runs for IMSM containers when they have array with redundancy so
if mdmon doesn't run, mdadm prints this error. This is misleading and
unnecessary. Just print it in WaitClean function.

The sock in WaitClean is deprecated so it is removed.

Link: https://bugzilla.redhat.com/show_bug.cgi?id=1375002
Signed-off-by: Mariusz Tkaczyk <mariusz.tkaczyk@intel.com>
Signed-off-by: Jes Sorensen <jsorensen@fb.com>