pidfile.New() was opening a file in /proc to determine if the owning
process still exists. Use syscall.OpenProcess() on Windows instead.
Other OSes may also need to be updated here.
Signed-off-by: John Starks <jostarks@microsoft.com>
Upstream-commit: 9e5b93565c8a10f4b06d2bcf61305fdfb7128628
Component: engine