wpa_supplicant service: restart instead of stop & start

We now wait for dhcpcd to acquire a lease but dhcpcd is restarted on
system activation. As wpa_supplicant is stopped while dhcpcd is
restarting a significant delay is introduced on systems with wireless
network connections only. This changes the wpa_supplicant service to
also be restarted together with dhcpcd in case both services were
changed.

nixos/modules/services/networking/wpa_supplicant.nix

···
       wants = [ "network.target" ];
       requires = lib.concatMap deviceUnit ifaces;
       wantedBy = [ "multi-user.target" ];
+      stopIfChanged = false;
 
       path = [ pkgs.wpa_supplicant ];