dhcpcd service: always want by multi-user

When default gateways were specified the service wasn't wanted by anything at
all before.

Changed files
+1 -1
nixos
modules
services
networking
+1 -1
nixos/modules/services/networking/dhcpcd.nix
···
in
{ description = "DHCP Client";
-
wantedBy = optional (!hasDefaultGatewaySet) "network-online.target";
+
wantedBy = [ "multi-user.target" ] ++ optional (!hasDefaultGatewaySet) "network-online.target";
after = [ "network.target" ];
wants = [ "network.target" ];