flexfiles: use per-mirror specified stateid for IO
rfc8435 says:
For tight coupling, ffds_stateid provides the stateid to be used by
the client to access the file.
However current implementation replaces per-mirror provided stateid with
by open or lock stateid.
Ensure that per-mirror stateid is used by ff_layout_write_prepare_v4 and
nfs4_ff_layout_prepare_ds.
Signed-off-by: Tigran Mkrtchyan <tigran.mkrtchyan@desy.de>
Signed-off-by: Rick Macklem <rmacklem@uoguelph.ca>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>