exclude hadoop system dependency

ambari depends on hadoop-annotation. Under linux, it sometimes activates a
maven profile that includes an explicit dependency on ${java.home}/../lib/tools.jar

This change excludes this dependency, since this jar is no longer
included with Java 9. It also seems seems unlikely that we would require
this dependency at runtime, since it is only enabled on some platforms.

extensions-contrib/ambari-metrics-emitter/pom.xml

@@ -61,6 +61,12 @@
           <groupId>org.codehaus.jackson</groupId>
           <artifactId>jackson-mapper-asl</artifactId>
         </exclusion>
+        <exclusion>
+          <!-- ambari depends on hadoop-annotations, which in turn depends on
+          ${java.home}/../lib/tools.jar, which was removed in Java 9+ -->
+          <groupId>jdk.tools</groupId>
+          <artifactId>jdk.tools</artifactId>
+        </exclusion>
       </exclusions>
     </dependency>
     <dependency>