remote: Rework reconnection code

[jansol]

Apparently the old reconnection code was reliant on undefined behaviour that does not work very well on Linux, which became apparent while benchmarking reconnection. Implemented a more correct solution with pipes for signaling between thread pairs instead, as well as a couple of drive-by fixes.

[jansol]

I'll see about a proper explanation of the socket thread logic later, possibly as a follow-up PR.

[pjaaskel]

Pls rebase.