sshpeer: clean up API for sshpeer.__init__ (API)
Our refactoring left the state of sshpeer.__init__ in a poor
state. "create" was no longer used. Process/pipe arguments were
passed poorly. "name" was really a URL.
This commit cleans all that up.
.. api::
sshpeer.sshpeer.__init__ now receives arguments describing an
existing connection instead of creating a connection itself.
Differential Revision: https://phab.mercurial-scm.org/D2032