Make run-jdwp-tests.sh kill zombie dalvikvm processes

We weren't killing zombie dalvikvm processes due to changes in how we
control the targets of the tests.

Follow up to Commit: 617c9c50

Test: ./art/tools/run-jdwp-tests.sh --mode=host
Bug: 67778411
Bug: 62821960
Change-Id: I014cb36b586b628e4916c4490bb8587561f70aec