JDWP: fail test if debuggee does not exit normally

Makes a test fail if the debuggee exits with an error. This prevents
from passing a test while the debuggee aborts (during runtime
shutdown for instance).

By default, we expect the debuggee to exit with code 0. The tests
related to VirtualMachine.Exit command (that forces the runtime to
exit with a given error code) can specify a different exit code with
JDWPUnitDebuggeeProcessWrapper.setExpectedExitCode method.

Bug: 22907762
Bug: 17941266
Change-Id: I1acd4a4251d8cb3a335e581aef1792ea1049ba74