ext4: Change the default behaviour on error

ext4 file system was by default ignoring errors and continuing. This
is not a good default as continuing on error could lead to file system
corruption. Change the default to mark the file system
readonly. Debian and ubuntu already does this as the default in their
fstab.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Acked-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>