ext4/050: support indirect as well as extent mapped journals

ext4/050: support indirect as well as extent mapped journals

Simplify the test and fix ext4/050 failures when running ext4 without
extents enabled (e.g., in ext3 emulation mode).

Instead of relying on parsing debugfs output's (which varies depending
on whether the journal inode is extent mapped or indirect block
mapped), use debugfs's "cat" command to get the contents of the
journal.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>