Older Pangolin installs: Make sure UDP 21820 and Gerbil is updated for clients to work

[oschwartz10612]

Just wanted to put this builtin out there for people who may find it.

If you are struggling with getting an error like Client last hole punch is too old or the clients apps are stuck registering on the new 1.14 or 1.15 versions of Pangolin this could be for you.

For the clients feature to work you need to have updated Gerbil to 1.3.0 and have UDP port 21820 open on the VPS firewall and in the docker compose file.

Older installs that predated the 21820 port being configured by default will need to make this change.

Make sure to docker compose up -d with these changes or restart the whole stack.