io: fix check for handshake completion in TLS test

The TLS I/O channel test had mistakenly used && instead
of || when checking for handshake completion. As a
result it could terminate the handshake process before
it had actually completed. This was harmless before but
changes in GNUTLS 3.6.0 exposed this bug and caused the
test suite to fail.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
