Guard publish of TUNNEL_IDENTIFIER as env var with a check to isUseGeneratedTunnelIdentifier(); if un-guarded, the speculatively-generated identifier is published when there is no intent to use it.
Merge branch 'TRE-2149-sfly-1.X-simplify-use-of-identified-tunnels' into sfly-1.X

Don't publish a tunnel-identifier unless asked.