tests/test-gendoc-it.t

sshpeer: inline I/O into _validaterepo()

We want to move the handshake code out of the peer class so the
peer factory function can perform the handshake and instantiate
a proper class depending on the results. To make that refactor
easier to read, we first inline I/O functionality into
_validaterepo().

Test output for low-level protocol tests didn't change, thus
hopefully demonstrating that this refactor didn't change any
material behavior.

Because we no longer call _callstream(), our test extension for
monkeypatching the peer had to change its hook point.

Differential Revision: https://phab.mercurial-scm.org/D2033

#require docutils gettext

  $ $TESTDIR/check-gendoc it
  checking for parse errors