Log matched issues at fine level to aid debugging

Change-Id: I0d305ab983e91a041161747da4cade27c72bc089
diff --git a/src/main/java/com/googlesource/gerrit/plugins/its/base/util/IssueExtractor.java b/src/main/java/com/googlesource/gerrit/plugins/its/base/util/IssueExtractor.java
index 6131ed4..acbc31c 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/its/base/util/IssueExtractor.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/its/base/util/IssueExtractor.java
@@ -88,6 +88,7 @@
     while (matcher.find()) {
       String issueId = matcher.group(groupIdx);
       if (!Strings.isNullOrEmpty(issueId)) {
+        logger.atFine().log("Matched issue id '%s'", issueId);
         issues.add(issueId);
       }
     }