Add DKTL_NO_PROXY flag that supresses starting the proxy on CI systems.

[grugnog]

[grugnog]

Setting DKTL_NO_PROXY=1 will prevent the proxy from starting and stopping - this is really only useful in CI systems where there is a central Traefik running (that conflicts with the dktl automated one) and probably not worth documenting unless we can think of someone else who might feasibly benefit from this.