DAFS: make FSYNC_VOL_QUERY_VOP DAFS-only

DAFS: make FSYNC_VOL_QUERY_VOP DAFS-only

all the support code handles this only for DAFS. the
case statement should treat as unknown if it is.

Reviewed-on: http://gerrit.openafs.org/3485
Reviewed-by: Jeffrey Altman <jaltman@openafs.org>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 7b7cd95ec0adc2c58b0387a5ff788251127f504e)

Change-Id: I74bf87d251663404e830f30fcbf47275b1aa468a
Reviewed-on: http://gerrit.openafs.org/3795
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>