Remove one-time use macros which check for the vnode lifecycle.  More,
some parts of the checks are in fact redundand in the surrounding
code, and it is more clear what the conditions are by direct testing
of the flags.  Two of the three macros were only used in assertions.

In vnlru_free(), all relevant parts of vholdl() were already inlined,
except the increment of v_holdcnt itself.  Do not call vholdl() to do
the increment as well, this allows to make assertions in
vholdl()/vhold() more strict.

In v_incr_usecount(), call vholdl() before incrementing other ref
counters.  The change is no-op, but it makes less surprising to see
the vnode state in debugger if interrupted inside v_incr_usecount().

Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week