connectionmanager: add isConnected

To check if we're connected with a device

Change-Id: I9d0659c3d6d5e305baabd5c4156a820754bae377
diff --git a/include/connectionmanager.h b/include/connectionmanager.h
index e11c27a..5a97280 100644
--- a/include/connectionmanager.h
+++ b/include/connectionmanager.h
@@ -140,6 +140,13 @@
     bool isConnecting(const DeviceId& deviceId, const std::string& name) const;
 
     /**
+     * Check if we are already connected to a device
+     * @param deviceId      Remote device
+     * @return if connected
+     */
+    bool isConnected(const DeviceId& deviceId) const;
+
+    /**
      * Close all connections with a current device
      * @param peerUri      Peer URI
      */