libsnapshot/test: Re-enable the failing tests

Some tests were temporarily disabled due to errors in Cuttlefish.
Now that the issues were fixed, the tests can be put back in presubmit.

Bug: 148889015
Test: vts_libsnapshot_test (Cuttlefish + Pixel 4)
Signed-off-by: Alessio Balsini <balsini@google.com>
Change-Id: Idcb2b7831b2183b2d734bdf8821fd34746f2beee