scripts/install-ubuntu.bash the installed service file should override the max file descriptors

[tburtchell]

The ubuntu service runs out of open file descriptors after running for a couple of days. The service files that we use for the controller and routers both override the number of file handles to 65535.

It would be great if the file installed by this script, ziti-edge-tunnel.service, provides the same change by adding

LimitNOFile=65535

[qrkourier]

We shouldn't do this in install-ubuntu.bash, but here's the template for ziti-edge-tunnel.service. If an appropriate universal value can be identified it can live there and will be inherited and all new and also existing installations for which the service unit remains unmodified by the user.

If there's not a universally-appropriate default, we can add a drop-in override for the service unit that makes it easy for users to set a limit without departing from the package-managed service unit, which demands conflict resolution during upgrade operations.

As a last resort, there are RedHat and Debian package-manager-specific scriptlets.