Fix: check the remote server connectivity before adding to map

1. replace boolean typed enable flag into enumeration status type
2. put the service in pending state, if the activation was failed

Change-Id: I15110f3d837d9a3ecf048c2777ec6fae9bf264ff
diff --git a/apps/openstacktelemetry/api/src/main/java/org/onosproject/openstacktelemetry/api/TelemetryAdminService.java b/apps/openstacktelemetry/api/src/main/java/org/onosproject/openstacktelemetry/api/TelemetryAdminService.java
index 63e0c3f..98b580d 100644
--- a/apps/openstacktelemetry/api/src/main/java/org/onosproject/openstacktelemetry/api/TelemetryAdminService.java
+++ b/apps/openstacktelemetry/api/src/main/java/org/onosproject/openstacktelemetry/api/TelemetryAdminService.java
@@ -24,8 +24,9 @@
      * Prepares and launches the telemetry producer.
      *
      * @param name telemetry service name
+     * @return true if the service is successfully started, false otherwise
      */
-    void start(String name);
+    boolean start(String name);
 
     /**
      * Terminates the telemetry producer.
@@ -38,8 +39,9 @@
      * Restarts the telemetry producer.
      *
      * @param name telemetry service name
+     * @return true if the service is successfully restarted, false otherwise
      */
-    void restart(String name);
+    boolean restart(String name);
 
     /**
      * Launches all telemetry services.