Skip tests if vendor partition is on Android S

Bug: 349278999
Test: vts_libsnapshot_test on GSI config
Signed-off-by: Akilesh Kailash <akailash@google.com>
(cherry picked from https://android-review.googlesource.com/q/commit:6906249312be46b64b6b6221ba33bad196bf6cd6)
Merged-In: I6826b287565e8a78bea21b4830ad30f1c30a01bf
Change-Id: I6826b287565e8a78bea21b4830ad30f1c30a01bf