NFS: Fix the setting of capabilities when automounting a new filesystem

[ Upstream commit b01f21cacde9f2878492cf318fee61bf4ccad323 ]

Capabilities cannot be inherited when we cross into a new filesystem.
They need to be reset to the minimal defaults, and then probed for
again.

Fixes: 54ceac45 ("NFS: Share NFS superblocks per-protocol per-server per-FSID")
Cc: stable@vger.kernel.org
Reviewed-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
[ adapted to older fs_context-less API structures ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>