lockd: fix decoding of TEST results

lockd: fix decoding of TEST results

[ Upstream commit b8db159239b3f51e2b909859935cc25cb3ff3eed ]

We fail to advance the read pointer when reading the stat.oh field that
identifies the lock-holder in a TEST result.

This turns out not to matter if the server is knfsd, which always
returns a zero-length field.  But other servers (Ganesha is an example)
may not do this.  The result is bad values in fcntl F_GETLK results.

Fix this.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>