Add a hint suggesting why tmpfs does not need a special case there.
The page read or written could be wired.  Do not requeue if the page
is not on a queue.

Reported and tested by:	pho
Sponsored by:	The FreeBSD Foundation
For the new regular tmpfs vnode, v_object is initialized before
insmntque() is called.  The standard insmntque destructor resets the
vop vector to deadfs one, and calls vgone() on the vnode.  As result,
v_object is kept unchanged, which triggers an assertion in the reclaim
code, on instmntque() failure.  Also, in this case, OBJ_TMPFS flag on
the backed vm object is not cleared.

Provide the tmpfs insmntque() destructor which properly clears
OBJ_TMPFS flag and resets v_object.

Reported and tested by:	pho
Sponsored by:	The FreeBSD Foundation
Fix the v_object leak for non-regular tmpfs vnodes.

Reported and tested by:	pho
Sponsored by:	The FreeBSD Foundation