gfs2: print details on transactions that aren't properly ended

If function gfs2_trans_begin is called with another transaction active
it BUGs out, but it doesn't give any details about the duplicate.
This patch moves function gfs2_print_trans and calls it when this
situation arises for better debugging.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>