Implement exponential back off for proxy

[ivcosla]

Current approach to get around proxy client app failure on startup is to retry on a fixed interval until it connects with the server (until there is a route).

This is not a good solution, as a workaround I propose to follow something similar to what we have for ssh: server app, client app and then cli. the cli will be in charge of starting a proxy connection to a given server, as well as stopping it.

This way proxy-client won't fail on startup if there is no route, the cli commands will fail if there is no route, but then there is responsibility for the user to try again if he wants to.

Since it is not failing at the moment I don't think this is a prioritary task, however I would like to hear opinions on this proposal or additional ones.

[gz-c]

anything with retry behavior should consider exponential backoff

[ivcosla]

the retries that we added to apps have exponential backoff, but for proxy we didn't, since it needs to retry until it works, time intervals would become very big.

Maybe a max timeout can be set and apply exponential backoff with such timeout as a maximum value.