DAFS: fix VOL_HDR_IN_LRU state bit tracking

DAFS: fix VOL_HDR_IN_LRU state bit tracking

For the case where the cached vp->header can be re-used by
GetVolumeHeader(), we have not been re-setting the VOL_HDR_IN_LRU
state bit.  Although this has not affected correctness (this
bit is merely used to aid in debugging), we should be resetting
it in all relevant cases...

Change-Id: I2ad2b8c5070470beb067efdcda6f76f6b72c006c
Reviewed-on: http://gerrit.openafs.org/2308
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>