security: don't provide default passwords

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

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

@@ -1,5 +1,10 @@
 #!/usr/bin/with-contenv bash
 
+if [[ -z $JIBRI_RECORDER_PASSWORD || -z $JIBRI_XMPP_PASSWORD ]]; then
+    echo 'FATAL ERROR: Jibri recorder password and auth password must be set'
+    exit 1
+fi
+
 # DISPLAY is necessary for start
 [ -z "${DISPLAY}" ] \
 && ( echo -e "\e[31mERROR: Please set DISPLAY variable.\e[39m"; kill 1; exit 1 )