btrfs-progs: add root to dirty list when fixing bad keys

btrfs-progs: add root to dirty list when fixing bad keys

A user reported a WARN_ON() when trying to run btrfsck --repair on his fs with
bad key ordering.  This was because the root that was broken wasn't part of the
transaction yet.  We do this open coded thing in a few other places in fsck, so
just make it a helper function and make sure all the places that need to call it
do call it.  With this patch he was able to run repair without it dying.
Thanks,

Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: David Sterba <dsterba@suse.cz>