e2fsck: add an option which causes it to only do a journal replay

e2fsck: add an option which causes it to only do a journal replay

As recently discussed on linux-ext4@vger.kernel.org add an option to e2fsck
to allow to replay the journal only. That will allow scripts, such as
pacemakers 'Filesystem' RA to first replay the journal and if that sets
an error state from the journal replay, further check for that error
(dumpe2fh -h | grep "Filesystem state:") and if that shows and error
to refuse to mount. It also allows automatic e2fsck scripts to first
replay the journal and on a second run after the real pass1 to passX checks
to test for the return code.

Signed-off-by: Bernd Schubert <bschubert@ddn.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>