With the new-and-improved vm_fault_copy_entry() (r265843), we can always
avoid soft page faults when adding write access to user wired entries in
vm_map_protect().  Previously, we only avoided the soft page fault when
the underlying pages were copy-on-write.  In other words, we avoided the
pages faults that might sleep on page allocation, but not the trivial
page faults to update the physical map.

Reviewed by:	kib
MFC after:	1 week
Sponsored by:	EMC / Isilon Storage Division
Fix locking.  The dst_object must remain locked on the retry of the
loop iteration.

Reported and tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	6 days