Postpone dropping fp till both kq_global and kqueue mutexes are unlocked. fdrop() closes file descriptor when reference count goes to zero. Close method for vnodes locks the vnode, resulting in "sleepable after non-sleepable". For pipes, pipe mutex is before kqueue lock, causing LOR.
Postpone dropping fp till both kq_global and kqueue mutexes are
unlocked. fdrop() closes file descriptor when reference count goes to
zero. Close method for vnodes locks the vnode, resulting in "sleepable
after non-sleepable". For pipes, pipe mutex is before kqueue lock,
causing LOR.

Reported and tested by:	pho
MFC after:	2 weeks

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