From: Ian Kent <raven@themaw.net>

The case where two process similtaneously trigger a mount in autofs4 can
cause multiple requests to the daemon for the same mount.  The daemon
handles this OK but it's possible an incorrect error to be returned.  For
this reason I believe it is better to change the spin lock to a semaphore
in waitq.c.  This makes the second and subsequent request wait on the q as
ther supposed to.