[Test] Fix LTP tests for sync_file_range02 and fdatasync03

[hukoyu]

Even if the two tests that I pointed out above sometimes pass, they are not implemented correctly. Given that, they are not testing anything useful.

• The test sync_file_range02 mounts an already mounted block device again.
• The test fdatasync03 tries to unmount a block device under an incorrect path.
• The enclave config mounts /dev/vdb under /data but this is not the path that the tests assume, and they are still trying to do their own mounting and unmounting.

@prp only these two tests have problem right? Also if you can provide more info to help solution that will be awesome.

[hukoyu]

Disabled fdatasync03 and sync_file_range02 LTP tests for now in PR #812