router - consider changing default tunnel mode to "host"

[qrkourier]

Default mode is "none" because the router will panic crash if it wasn't created with tunneler enabled. This means that existing routers upgrading to a chart with default mode "host" will fail to start after the upgrade unless they happen to have tunneler administratively enabled.

If default IS changed, then update doc section "Host tunnel mode" and publish the intervention to enable tunneling on an existing router:

ziti edge update edge-router "router1" \
   --tunneler-enabled

ziti edge update identity "router1" \
    --role-attributes acme-hosts

Also, if changing the default, some impact is expected, so inform the team about this problem.

Consider changing the router's behavior in this issue to avoid panic if tunneler NOT administratively enabled: openziti/ziti#2238