Addres GCE instance cleanup and connection issues in windows-builder.

[isarkis]

In our tests, it can take up to 20 mins for windows-builder to be able to connect to GCE instance. Increasing timeout from 5 to 25 mins.

RunDef() function is used to check if server is online. Sometimes, RunDef() hangs for 10-20 mins before GCE API times out. To avoid this condition, setting custom function timeout handler.

Under certain circumstances, when builds fail, windows-builder doesn't delete GCE instance because termination signal handler hasn't been set yet. Setting termination signal handler just after GCE instance is created should handle these corner cases.