build: Enabling -Werror in debug mode and fixing discovered issues

Change-Id: I29685dcb9240a3e0c8d7eaf28c8bc2ae720e55a1
diff --git a/daemon/mgmt/face-manager.cpp b/daemon/mgmt/face-manager.cpp
index 96d1ce7..4028ad5 100644
--- a/daemon/mgmt/face-manager.cpp
+++ b/daemon/mgmt/face-manager.cpp
@@ -317,6 +317,9 @@
           try
             {
               keepAliveInterval = i->second.get_value<size_t>();
+
+              /// \todo Make use of keepAliveInterval
+              (void)(keepAliveInterval);
             }
           catch (const std::exception& e)
             {