[product: zaphod][project: zaphod-v0.3]: Implemented stop VM.

SYNOPSIS
[modified]m42/test/test_zaphod.py: Test for stopvm.
[modified]m42/test/vmguard.py: VM guard that automatically starts a VM.
[modified]m42/test/zaphodtestutil.py: Start VMs. Check that they are running.
[modified]m42/zaphod.py: Implemented stopvm.

DETAILS
Implemented Zaphod.stopvm that stops a runningvm. Testing for a stoppedvm
needs code to start a VM and then check that is running. The changes
to the test code reflect that need.