...and convert existing cifs users of system_nrt_wq to use that instead.

Also, make it freezable, and set WQ_MEM_RECLAIM since we use it to
deal with write reply handling.
Signed-off-by: NJeff Layton <jlayton@redhat.com>
Acked-by: NShirish Pargaonkar <shirishpargaonkar@gmail.com>