Improve the test_serf_ssl_client_certificate test by verifying that both client_cert and client_cert_pw callbacks are called.
Improve the test_serf_ssl_client_certificate test by verifying that both
client_cert and client_cert_pw callbacks are called.

* test/test_context.c:
  (TEST_RESULT_CERTCB_CALLED)
  (TEST_RESULT_CERTCHAINCB_CALLED): Rename to TEST_RESULT_SERVERCERT*.
  (TEST_RESULT_CLIENT_CERTCB_CALLED,
   TEST_RESULT_CLIENT_CERTPWCB_CALLED): New defines.
  (ssl_server_cert_cb_expect_failures,
   ssl_server_cert_cb_expect_allok,
   cert_chain_cb,
   test_serf_ssl_certificate_chain): Update to use the renamed codes.
  (client_cert_cb,
   client_cert_pw_cb): Make note in result bitmask that function was called.
  (test_serf_ssl_client_certificate): Check that both callback functions were
       called.
   
jandre/serf,jandre/serf,jandre/serf,jandre/serf