ext4: create file systems with the encrypt feature as necessary

ext4: create file systems with the encrypt feature as necessary

The linux kernel commit 5f41fdaea63d ("ext4: only allow
test_dummy_encryption when supported") the kernel will reject mounts
with the test_dummy_encryption option if the ext4 file system does not
have the encrypt feature enabled.

There are a handful of tests (ext4/003, ext4/035, ext4/306, and
generic/260) which will format the scratch file system using a
hard-coded set of mkfs.ext4 parameters ignoring the MKFS_OPTION that
is set by the file system test config.

For file system configs which includes test_dummy_encryption in
MOUNT_OPTIONS and "-O encrypt" in MKFS_OPTIONS, we need to test for
test_dummy_encryption and force the hard-coded mkfs options to enable
the encrypt feature.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>