MFC r272403:

Make autofs timeout handling use timeout task instead of callout;
that's because the handler can sleep on sx lock.

Sponsored by:	The FreeBSD Foundation
MFC r272405:

Call uma_zfree() outside of lock, and improve comment.

Sponsored by:	The FreeBSD Foundation
MFC r272470:

Make autofs(4) use shared lock for lookups, instead of exclusive one.

Sponsored by:	The FreeBSD Foundation
MFC r272471:

Fix autofs debug macros.

Sponsored by:	The FreeBSD Foundation
MFC r272512:

Make autofs use shared vnode locks.

Sponsored by:	The FreeBSD Foundation
MFC r272743:

Simplify; no functional changes.

Sponsored by:	The FreeBSD Foundation
MFC r272836:

Remove remnants of some cleanup; no functional changes.

Sponsored by:	The FreeBSD Foundation
MFC r272931:

Add assertion to catch duplicated nodes.

Sponsored by:	The FreeBSD Foundation