nixos/tests: fix gitdaemon under network-online dep fix

Changed files
+3
nixos
+3
nixos/tests/gitdaemon.nix
···
with subtest("git daemon starts"):
server.wait_for_unit("git-daemon.service")
+
+
server.systemctl("start network-online.target")
+
client.systemctl("start network-online.target")
server.wait_for_unit("network-online.target")
client.wait_for_unit("network-online.target")