Windows: AFSWriteCommon collapse redundant condition

Windows: AFSWriteCommon collapse redundant condition

We never get non cached and yet paging IO.  Even if we did it would
be inappropriate to call CcCanIWrite.  Therefore, collapse two if
statements into one.

Change-Id: I95c9030836e4f7dc4f7867a8b8b09b97bf57b429
Reviewed-on: http://gerrit.openafs.org/9125
Reviewed-by: Rod Widdowson <rdw@steadingsoftware.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Peter Scott <pscott@kerneldrivers.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>