jenkins service: improve curl call in postStart

* Perform HTTP HEAD request instead of full GET (lighter weight)
* Don't log output of curl to the journal (it's noise/debug)
* Use explicit http:// URL scheme
* Reduce poll interval from 10s to 2s (respond to state changes
quicker). Probably not relevant on boot (lots of services compete for
the CPU), but online service restarts/reloads should be quicker.
* Pass --fail to curl (should be more robust against false positives)
* Use 4 space indent for shell code.

Changed files
+2 -2
nixos
modules
services
continuous-integration
jenkins
+2 -2
nixos/modules/services/continuous-integration/jenkins/default.nix
···
'';
postStart = ''
-
until ${pkgs.curl.bin}/bin/curl -s -L ${cfg.listenAddress}:${toString cfg.port}${cfg.prefix} ; do
-
sleep 10
done
'';
···
'';
postStart = ''
+
until ${pkgs.curl.bin}/bin/curl -s -L --fail --head http://${cfg.listenAddress}:${toString cfg.port}${cfg.prefix} >/dev/null; do
+
sleep 2
done
'';