task: Rewrite method to make it look less buggy

A for loop that always returns the first element looks suspicious (and
in fact is flagged by SonarQube). We can write this more clearly using
an iterator.

Change-Id: I9d7191dc78deec17b115b304c69339dde04a5e16

src/main/java/com/googlesource/gerrit/plugins/task/Properties.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/task/Properties.java b/src/main/java/com/googlesource/gerrit/plugins/task/Properties.java
index 56bf23f..c68349f 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/task/Properties.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/task/Properties.java
@@ -27,6 +27,7 @@
 import java.util.List;
 import java.util.ListIterator;
 import java.util.Map;
+import java.util.NoSuchElementException;
 import java.util.Set;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
@@ -114,10 +115,11 @@
   }
 
   protected String getFirstUnexpandedProperty() {
-    for (String property : unexpanded.keySet()) {
-      return property;
+    try {
+      return unexpanded.keySet().iterator().next();
+    } catch (NoSuchElementException e) {
+      return null;
     }
-    return null;
   }
 
   protected void expandInPlace(List<String> list) {