Fix ssh.process not setting ssh_process.cwd

[peace-maker]

The cwd wasn't passed to the ssh_process created in ssh.process, so the ssh_process.cwd attribute was never set. The process is running in the correct working directory though, but the cwd attribute didn't reflect it.

This passes the cwd along now.

s = ssh(..)
io = s.process("pwd", cwd="/tmp")
io.cwd # was ".", is now "/tmp"
io.recvall() # b"/tmp\n"

Fixes #1479

[Arusekk]

I'm not sure what we should do with wd= vs cwd= in general, and should this be considered an API change (because no matter how bugfixy it is, we cannot push it to stable, because it would kill our semantic versioning).

[peace-maker]

Depends on if we consider ssh_channel public API. I don't know how you would use it directly without going though ssh.

[Arusekk]

Okay, but I think we should clean up this process(cwd=...) vs system(wd=...) thing on dev branch while at it.

[peace-maker]

Yes, but that would be a breaking change. 😄 Are we fine with those in minor versions?

[Arusekk]

I thought more like allowing both new and old way, and deprecating the old way.