acquire vnode lock for OBJT_VNODE object after map lock is dropped.
Because we have the busy page(s) in the object, sleeping there would
result in deadlock with vnode resize. Try to get lock without sleeping,
and, if the attempt failed, drop the state, lock the vnode, and restart
the fault handler from the start with already locked vnode.
Because the vnode_pager_lock() function is inlined in vm_fault(),
axe it.
Based on suggestion by: alc
Reviewed by: tegge, alc
Tested by: pho
d2bf64c309