Avoid long overflow in AccessToken#isExpired()

Change-Id: Ia21fe609f63f9b069dfd37e9b90e4cb59e6c4ab2
Signed-off-by: Michael Ochmann <michael.ochmann@sap.com>
diff --git a/src/main/java/com/googlesource/gerrit/plugins/cfoauth/AccessToken.java b/src/main/java/com/googlesource/gerrit/plugins/cfoauth/AccessToken.java
index a9af673..9ea32ed 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/cfoauth/AccessToken.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/cfoauth/AccessToken.java
@@ -72,7 +72,7 @@
    * Returns <code>true</code> if this token has already expired.
    */
   boolean isExpired() {
-    return System.currentTimeMillis() > expiresAt * 1000;
+    return System.currentTimeMillis() / 1000L >  expiresAt;
   }
 
   /**