CA config and Client config: update format and semantics of probe

Refs: https://github.com/named-data/ndncert/wiki/NDNCERT-CA-Configuration

Change-Id: Ia0a8def6aea8565533a0f5364c44768d3849f18f
diff --git a/tests/unit-tests/ca-config.t.cpp b/tests/unit-tests/ca-config.t.cpp
index 78aa9da..0e53dff 100644
--- a/tests/unit-tests/ca-config.t.cpp
+++ b/tests/unit-tests/ca-config.t.cpp
@@ -38,7 +38,7 @@
   BOOST_CHECK_EQUAL(config.m_caName.toUri(), "/ndn");
   BOOST_CHECK_EQUAL(config.m_freshnessPeriod, time::seconds(720));
   BOOST_CHECK_EQUAL(config.m_validityPeriod, time::days(360));
-  BOOST_CHECK_EQUAL(config.m_probe, "input email address");
+  BOOST_CHECK_EQUAL(config.m_probe, "");
   BOOST_CHECK_EQUAL(config.m_caInfo, "ndn testbed ca");
 }