Per file descriptor TID caching actions depend on a global that can
change midway through the lifetime of that file descriptor.

Make the use of caching consistent for the life of the file descriptor
by using the presence of the cache handler to decide when to use the cache
functions.
Reviewed-by: NIra Weiny <ira.weiny@intel.com>
Signed-off-by: NDean Luick <dean.luick@intel.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>