Fix blkid library so that the cache validation notices ext2 to ext3 conversion

Fix blkid library so that the cache validation notices ext2 to ext3 conversion

There's mistake in blkid ext2 detection code. The libblkid doesn't
check for journal when revalidate the cache information about an ext2
device.

        # rm -f /etc/blkid.tab

        # mkfs.ext2 /dev/loop0 &> /dev/null
        # blkid -s TYPE /dev/loop0
        /dev/loop0: TYPE="ext2"

        # mkfs.ext3 /dev/loop0 &> /dev/null
        # blkid -s TYPE /dev/loop0
        /dev/loop0: TYPE="ext2"

That bug doesn't appear when libblkid creates new cache and checks for
all possible filesystems, because it tries ext3 before ext2. BUT when
the library only revalidate the cache it first probes for old cached
filesystem (e.g. ext2).

Signed-off-by: Karel Zak <kzak@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>