NFSv4.1 query for fs_location attr on a new file system

NFSv4.1 query for fs_location attr on a new file system

[ Upstream commit 1976b2b31462151403c9fc110204fcc2a77bdfd1 ]

Query the server for other possible trunkable locations for a given
file system on a 4.1+ mount.

v2:
-- added missing static to nfs4_discover_trunking,
reported by the kernel test robot

Signed-off-by: Olga Kornievskaia <kolga@netapp.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>