GFS2: Combine transaction from gfs2_dir_exhash_dealloc

At the end of function gfs2_dir_exhash_dealloc, it was setting the dinode
type to "file" to prevent directory corruption in case of a crash.
It was doing so in its own journal transaction.  This patch makes the
change occur when the last call is make to leaf_dealloc, since it needs
to rewrite the directory dinode at that time anyway.

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