f2fs/016: add test cases for test_dummy_encryption mount option

f2fs/016: add test cases for test_dummy_encryption mount option

Add test cases to verify f2fs's support for different versions of the
"test_dummy_encryption" mount option.

To ensure test robustness, the MKFS_OPTIONS and MOUNT_OPTIONS are
cleared. This prevents additional options from interfereing with the
test results.

Signed-off-by: Joanne Chang <joannechien@google.com>
Reviewed-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Zorro Lang <zlang@kernel.org>