common/rc: ext4 doesn't support O_DIRECT with data journaling

common/rc: ext4 doesn't support O_DIRECT with data journaling

Modify _require_odirect() to skip O_DIRECT tests if the ext4 mount
option data=journal has been applied.  Because ext4 disables its
O_DIRECT support when in data journaling mode, no significant value
is obtained by running these tests and they consume a significant
amount of run time.  Additionally, this change eliminates the need
to triage false negative O_DIRECT test results caused by test
problems, as has occurred from time to time.

Signed-off-by: Eric Whitney <enwlinux@gmail.com>
Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Eryu Guan <eguan@redhat.com>