jbd2: rename obsoleted msg JBD->JBD2

Rename performed via: perl -pi -e 's/JBD:/JBD2:/g' fs/jbd2/*.c

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>