tests: use LC_LIBSSH instead of LANG for env tests.

LANG is stripped and replaced on many distros and LC_* is accepted
by default on debian
socket: don't attempt reading a non-connected socket
poll: fix poll_handles ownerships
session: Fix a possible memory leak.
tests: auth_agent_nonblocking should run in nonblocking
test: test case for async auth_none

This test currently fails
test: fixed torture_auth_none condition