Proxies template change breaks connections

[ValentaTomas]

When we change the template in the client or session proxy the proxy should have been just reloaded without breaking connections.

Right now it looks like Nomad restarts the container and breaks all existing WS connections to sandboxes.

[ValentaTomas]

This might be caused by the default config of Nginx proxies that limits the proxies to 1 worker.

[ValentaTomas]

The number of workers cannot be configured while using load-balancer config — we need to change the Nomad job configuration to be able to fix this.

[ValentaTomas]

This should be fixed in #166 but we need to test it.