common: rework _require_ext4_mkfs_feature

common: rework _require_ext4_mkfs_feature

In all of the places where we need check to see if mkfs.ext4 can
support a set of file system features, we also should be checking to
see if the kernel can support those file system features.  So rename
_require_ext4_mkfs_feature to _require_scratch_ext4_feature, and
actually format the file system in $SCRATCH_DEV.

Also allow ext4/306 to run on systems where mke2fs doesn't support
the "64bit" option.

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