Added protections for RenderScript VTS tests.

Changed many EXPECT_NE to ASSERT_NE for objects that are required later
in the test which would potentially cause a segfault. Additionally updated
a few descriptions.

Bug: 35915961

Test: mm and run on angler
Change-Id: I17c85b2c774688d82b59be2f0b383447e03349e0
(cherry picked from commit b2039ad7)