Various improvements and bug fixes

- Watch more events for lease file changes
 - Improving network up detection by using bootstrap IPv6 along side
   IPv4 one.
 - Emitting log to notice user that ctrld is starting.
 - Using systemd wrapper to provide correct status.
 - Restoring DNS on stop on Windows.

internal/clientinfo/dhcp.go

@@ -53,7 +53,7 @@ func (d *dhcp) watchChanges() {
 			if !ok {
 				return
 			}
-			if event.Has(fsnotify.Write) {
+			if event.Has(fsnotify.Write) || event.Has(fsnotify.Rename) || event.Has(fsnotify.Chmod) || event.Has(fsnotify.Remove) {
 				format := clientInfoFiles[event.Name]
 				if err := d.readLeaseFile(event.Name, format); err != nil && !os.IsNotExist(err) {
 					ctrld.ProxyLogger.Load().Err(err).Str("file", event.Name).Msg("leases file changed but failed to update client info")