[GFS2] Fix a couple of refcount leaks.

recovery.c add a brelse to deal with gfs2_replay_read_block being called
twice on the same block.

add a dput to drop the ref count on the root inode.
This was causing lingering glocks and thus causing
a mount failure to hang.

Fix a endian conversion macro that was was swizzling
16bits when it should have been swizzling 32.

Signed-off-by: Russell Cattelan <cattelan@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>