[lib] Pass keyserverID to Socket

Summary: In the next diff, I'll use this keyserverID in place of ashoatKeyserverID. This will be a no-op, since KeyserverConnectionHandler currently only renders a Socket when keyserverID === ashoatKeyserverID.

Test Plan:

1. Flow
2. Careful inspection of the code

Reviewers: inka, tomek

Reviewed By: inka

Differential Revision: https://phab.comm.dev/D11012