ext2fs_flushfs: Remove the NEEDS_RECOVERY from the backup superblocks

ext2fs_flushfs: Remove the NEEDS_RECOVERY from the backup superblocks

Now that e2fsck tries to backup the primary superblock to the backups
when the feature sets ar different, it's important when tune2fs writes
out a changed superblock, that we filter out the
EXT3_FEATURE_INCOMPAT_RECOVER feature to the backup superblocks, since
it will be removed from the primary superblock either when the
filesystem is mounted uncleanly or when journal is replayed.

Addresses-Debian-Bug: #454926

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>