[GFS2] return conflicts for GETLK

We weren't returning the correct result when GETLK found a conflict,
which is indicated by userspace passing back a 1.

Signed-off-by: Abhijith Das <adas redhat com>
Signed-off-by: David Teigland <teigland redhat com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>