NFSD: fix setting FMODE_NOCMTIME in nfs4_open_delegation

NFSD: fix setting FMODE_NOCMTIME in nfs4_open_delegation

fstests generic/215 and generic/407 were failing because the server
wasn't updating mtime properly. When deleg attribute support is not
compiled in and thus no attribute delegation was given, the server
was skipping updating mtime and ctime because FMODE_NOCMTIME was
uncoditionally set for the write delegation.

Fixes: e5e9b24ab8fa ("nfsd: freeze c/mtime updates with outstanding WRITE_ATTRS delegation")
Cc: stable@vger.kernel.org
Signed-off-by: Olga Kornievskaia <okorniev@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>