Windows: Always AFSInitFcb and AFSRemoveFcb

Windows: Always AFSInitFcb and AFSRemoveFcb

Instead of comparing ObjectInfo->Fcb to NULL and conditionally
calling AFSInitFcb() or AFSRemoveFcb(), always call them and use
InterlockedExchangePointer() as the test.

Change-Id: I81915dfdfdf180c04ad2b4ff7506784a83ee8c2a
Reviewed-on: http://gerrit.openafs.org/8221
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Rod Widdowson <rdw@steadingsoftware.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: Jeffrey Altman <jaltman@your-file-system.com>