- Fix PG_UNMANAGED compile problem on HEAD after r224746.
Remove explicit initialization of m->flags and m->oflags because per
default vm_phys_alloc_contig() already initializes the page as unmanaged.
Chase move of PG_UNMANAGED flag from m->flags to m->oflags and renaming
to VPO_UNMANAGED for an additional assert.
Reported by: Kyryll A Mirnenko <firstname.lastname@example.org>,
Michael Butler <email@example.com>
Thanks to: beat