wgengine/router/router_linux.go: fixed " route del failed" error (#756)

* wgengine/router/router_linux.go: Switched `cidrDiff("addr")` and `cidrDiff("route")` order

Signed-off-by: Christina Wen <christina@tailscale.com>

Co-authored-by: Christina Wen <christina@tailscale.com>

wgengine/router/router_linux.go

@@ -173,17 +173,17 @@ func (r *linuxRouter) Set(cfg *Config) error {
 		return err
 	}
 
-	newAddrs, err := cidrDiff("addr", r.addrs, cfg.LocalAddrs, r.addAddress, r.delAddress, r.logf)
+	newRoutes, err := cidrDiff("route", r.routes, cfg.Routes, r.addRoute, r.delRoute, r.logf)
 	if err != nil {
 		return err
 	}
-	r.addrs = newAddrs
+	r.routes = newRoutes
 
-	newRoutes, err := cidrDiff("route", r.routes, cfg.Routes, r.addRoute, r.delRoute, r.logf)
+	newAddrs, err := cidrDiff("addr", r.addrs, cfg.LocalAddrs, r.addAddress, r.delAddress, r.logf)
 	if err != nil {
 		return err
 	}
-	r.routes = newRoutes
+	r.addrs = newAddrs
 
 	switch {
 	case cfg.SNATSubnetRoutes == r.snatSubnetRoutes: