Split daemon service code to _windows file

This moves some of the code that was conditionally
executed on Windows to a separate, windows-only file.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

cmd/dockerd/docker_unix.go

@@ -0,0 +1,8 @@
+// +build !windows
+
+package main
+
+func runDaemon(opts *daemonOptions) error {
+	daemonCli := NewDaemonCli()
+	return daemonCli.start(opts)
+}