GFS2: Set gl_object during inode create

This patch fixes a cluster coherency problem that occurs when one
node creates a file, does several writes, then a different node
tries to write to the same file. When the inode's glock is demoted,
the inode wasn't synced to the media properly because the gl_object
wasn't set. Later, the flush daemon noticed the uncommitted data
and tried to flush it, only to discover the glock was no longer locked
properly in exclusive mode. That caused an assert withdraw.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>