common/rc: accept "localdomain" to mean YP/NIS disabled

common/rc: accept "localdomain" to mean YP/NIS disabled

When asked to 'cat' the passwd or group files, currently xfstests runs
the 'domainname' program to get what the kernel thinks the domainname
is.  It seems that traditionally this has been "(none)" if YP/NIS is not
in use.  However, Android devices use a different convention which is to
set the domainname to "localdomain".  Therefore, this patch updates
xfstests to accept both conventions to indicate YP/NIS disabled.  This
stops a number of tests from failing when run on Android.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>