Revert "Revert "tools: Fix art script to delete OAT files before running dalvikvm""

Now passes through the 'dalvikvm' exit code, which will fix the broken
JDWP tests.

This reverts commit 800421b2.

Bug: 64162479
Change-Id: I1cd924e32ac079f3f9e625a458c0606298c8e89b
Original-Change-Id: Ief1784b48c78464da91e71a649a6cf4b57c51b41