ProjectConfig#saveLabelSections: Save "branch" values

The branch values were not set in the config before saving, resulting
in the values being omitted from the config.

Change-Id: I95da7e27189558f98bd62c172e319be233b7b568

gerrit-server/src/main/java/com/google/gerrit/server/git/ProjectConfig.java

@@ -1340,6 +1340,11 @@ public class ProjectConfig extends VersionedMetaData implements ValidationError.
         values.add(value.format());
       }
       rc.setStringList(LABEL, name, KEY_VALUE, values);
+
+      List<String> refPatterns = label.getRefPatterns();
+      if (refPatterns != null && !refPatterns.isEmpty()) {
+        rc.setStringList(LABEL, name, KEY_BRANCH, refPatterns);
+      }
     }
 
     for (String name : toUnset) {