virt script timeout is implemented incorrectly

[Jeff Lane ]

the current implementation that boots the VM is this:

 # Boot Virtual Machine
 instance = self.boot_image(self.image)

 time.sleep(self.timeout)
 # If running in console, reset console window to regain
 # control from VM Serial I/0

This, unfortunately, makes the test run a lot longer than necessary.

Instead, we should run it so that the boot is kicked off and then we poll the output file every X seconds until timeout is reached.

That way, if we get the CERTIFICATION BOOT COMPLETE message before the timeout, we can exit the loop and proceed without waiting the full timeout time, OR we just time out, check one last time for the message and error if we don't see it.