HADOOP-15110. Gauges are getting logged in exceptions from AutoRenewalThreadForUserCreds.

Contributed by LiXin Ge.

(cherry picked from commit 3c9d97b8f7d6eb75f08fc6d37cee37c22760bb86)

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/lib/MutableGaugeFloat.java

@@ -77,4 +77,11 @@ public class MutableGaugeFloat extends MutableGauge {
       }
     }
   }
+
+  /**
+   * @return  the value of the metric
+   */
+  public String toString() {
+    return value.toString();
+  }
 }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/lib/MutableGaugeInt.java

@@ -87,4 +87,11 @@ public class MutableGaugeInt extends MutableGauge {
       clearChanged();
     }
   }
+
+  /**
+   * @return  the value of the metric
+   */
+  public String toString() {
+    return value.toString();
+  }
 }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/metrics2/lib/MutableGaugeLong.java

@@ -88,4 +88,10 @@ public class MutableGaugeLong extends MutableGauge {
     }
   }
 
+  /**
+   * @return  the value of the metric
+   */
+  public String toString() {
+    return value.toString();
+  }
 }