FBSD: catch up with the disappearance of VOP_GETVOBJECT

FBSD: catch up with the disappearance of VOP_GETVOBJECT

The vnode operation VOP_GETVOBJECT disappeared in FreeBSD 6.0, an
embarrassingly long time ago.  Six years ago, a kluge was added
to emulate its behavior, but it did not correctly emulate the
return value of the old VOP implementation.  As a result,
osi_VM_StoreAllSegments() could never actually do anything.  Since we
don't support FreeBSD before 8.0, remove all references to VOP_GETVOBJECT
and examine vp->v_object directly instead.

This has the result that osi_VM_StoreAllSegments() will actually do
something now, which may not be desirable.  (Previously, if somehow
the vnode had no associated VM object, it would crash, and otherwise
it would do nothing at all.)

Found-by: clang static analyzer
Reviewed-on: http://gerrit.openafs.org/5183
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 7d0cd1393ff5c69cba2f14fc76aa8f7ca588ccc3)

Change-Id: I57198967ad022f50af073ac43643f3a55b0801ef
Reviewed-on: http://gerrit.openafs.org/5187
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>