Partial revert of ag/3125606

Changes to the clearkey plugin broke existing vts
tests, and those tests can't be changed due to
backward compatibility requirements.  This CL
reverts the parts of ag/3125606 that caused the
test failures, while retaining most of those
changes.

bug:70660219

Test: vts-tradefed run commandAndExit vts -m VtsHalDrmV1_0Target
Change-Id: Iab54b0917cc2e1edafc98bd97390bf9937b3d2ca