face: MulticastEthernetTransport: remove promiscuous mode fallback

Change-Id: I040704577e66951ab5d1298ac4f99d98af11f809
Refs: #4081
diff --git a/daemon/face/multicast-ethernet-transport.hpp b/daemon/face/multicast-ethernet-transport.hpp
index 6ef893b..b89e88b 100644
--- a/daemon/face/multicast-ethernet-transport.hpp
+++ b/daemon/face/multicast-ethernet-transport.hpp
@@ -47,9 +47,8 @@
 private:
   /**
    * @brief Enables receiving frames addressed to our MAC multicast group
-   * @return true if successful, false otherwise
    */
-  bool
+  void
   joinMulticastGroup();
 
 private: