md_monitor: Fixup 'ArrayStatus' display

The output from 'ArrayStatus' is garbled. Fix it.

Signed-off-by: Hannes Reinecke <hare@suse.de>
md_monitor: use select when receiving CLI reply

CLI replies have a noticeable delay, as the initial
recvmsg is greeted with an EAGAIN. So better use
select() here to get an instantaneous reply.

Signed-off-by: Hannes Reinecke <hare@suse.de>