volume_inline.h: Down with assert, again

Commit 34767c6a0f914960c9a1efabe69dd9c312a2b400 replaced all assert
calls in this file with osi_Assert, but shortly thereafter, commit
db6ee95864a8fc5f33b7e95c19c8ff5058d37e92 added VTimedWaitStateChange_r
with two new assert calls.  These are precarious in a public header;
fix them to osi_Assert like the ones in VWaitStateChange_r.

Signed-off-by: Anders Kaseorg <andersk@mit.edu>
Reviewed-on: http://gerrit.openafs.org/10094
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
(cherry picked from commit 30fa9480dd99ed93fa642dd8ce9746760fb42180)

Change-Id: Id0bc0e75de000cf3e4133aaf31f52d9a565c8d9f
Reviewed-on: http://gerrit.openafs.org/10095
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>