NFSv4: Fix NFSv4 reference counting for trunked sessions

NFSv4: Fix NFSv4 reference counting for trunked sessions

commit 4ae19c2dd713edb7b8ad3d4ab9d234ed5dcb6b98 upstream.

The reference counting in nfs4_init_client assumes wongly that it
is safe for nfs4_discover_server_trunking() to return a pointer to a
nfs_client prior to bumping the reference count.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Chuck Lever <chuck.lever@oracle.com>
Cc: Ben Greear <greearb@candelatech.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>