jvb: Can't disable STUN in JVB because of default value

[HansGeiz]

JVB_STUN_SERVERS can't be empty and it is not possible to disable STUN.

/jvb/rootfs/defaults/jvb.conf:
...
{{ $JVB_STUN_SERVERS := .Env.JVB_STUN_SERVERS | default "meet-jit-si-turnrelay.jitsi.net:443" -}}
...
ice4j {
harvest {
mapping {
stun {
{{ if $JVB_STUN_SERVERS -}}
addresses = [ "{{ join "","" (splitList "," $JVB_STUN_SERVERS) }}" ]
{{ else -}}
enabled = false
{{ end -}}

[saghul]

Good point.