Fix gcc build.

Sponsored by:	The FreeBSD Foundation
MFC after:	13 days
Fix spurious "child process X terminated with exit status 1" messages
from automountd(8).

MFC after:	1 month
Sponsored by:	The FreeBSD Foundation
Fix bug that made automount(8) never unmount stale autofs(5) mounts,
ie mounts for entries that were there in auto_master(5), and then
got removed.

MFC after:	1 month
Sponsored by:	The FreeBSD Foundation