security: don't provide default passwords

Also check if they are not provided at sstartup time and fail to start
in that case.

jicofo/rootfs/etc/cont-init.d/10-config

@@ -1,5 +1,10 @@
 #!/usr/bin/with-contenv bash
 
+if [[ -z $JICOFO_COMPONENT_SECRET || -z $JICOFO_AUTH_PASSWORD ]]; then
+    echo 'FATAL ERROR: Jicofo component secret and auth password must be set'
+    exit 1
+fi
+
 if [[ ! -f /config/sip-communicator.properties ]]; then
     tpl /defaults/sip-communicator.properties > /config/sip-communicator.properties
 fi
@@ -8,4 +13,4 @@ if [[ ! -f /config/logging.properties ]]; then
     cp /defaults/logging.properties /config
 fi
 
-chown -R jicofo:jitsi /config
+chown -R jicofo:jitsi /config