Use correct plugin config for association policy

Use of the association policy at commentLink level was an
illegal hijack of Gerrit's native configuration features.

It is much better to use the canonical place dedicated to plugins.

Change-Id: I1b0c62b840b72d82949c4b6b8a555b292f0cc0fc
diff --git a/src/main/java/com/googlesource/gerrit/plugins/its/jira/InitJira.java b/src/main/java/com/googlesource/gerrit/plugins/its/jira/InitJira.java
index 38c4fe5..e0c8bea 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/its/jira/InitJira.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/its/jira/InitJira.java
@@ -104,7 +104,10 @@
     jiraComment.string("Jira issue-Id regex", "match", "([A-Z]+-[0-9]+)");
     jiraComment.set("html",
         String.format("<a href=\"%s/browse/$1\">$1</a>", jiraUrl));
-    jiraComment.select("Issue-id enforced in commit message", "association",
+
+    Section pluginConfig = sections.get("plugin", pluginName);
+
+    pluginConfig.select("Issue-id enforced in commit message", "association",
         ItsAssociationPolicy.SUGGESTED);
   }