fix bug for tag

Signed-off-by: liukun4515 <liukun@apache.org>

Author: liukun4515

simpleclient_graphite_bridge/src/main/java/io/prometheus/client/bridge/Graphite.java

@@ -61,7 +61,7 @@ public void push(CollectorRegistry registry) throws IOException {
         writer.write(m.replaceAll("_"));
         for (int i = 0; i < sample.labelNames.size(); ++i) {
           m.reset(sample.labelValues.get(i));
-          writer.write("." + sample.labelNames.get(i) + "." + m.replaceAll("_"));
+          writer.write(";" + sample.labelNames.get(i) + "=" + m.replaceAll("_"));
         }
         writer.write(" " + sample.value + " " + now + "\n");
       }

simpleclient_graphite_bridge/src/test/java/io/prometheus/client/bridge/GraphiteTest.java

@@ -50,7 +50,7 @@ public void run() {
     // Check result.
     String[] parts = result.toString().split(" ");
     assertEquals(3, parts.length);
-    assertEquals("labels.l.fo_o", parts[0]);
+    assertEquals("labels;l=fo_o", parts[0]);
     assertEquals("1.0", parts[1]);
     Integer.parseInt(parts[2]);  // This shouldn't throw an exception.
   }