testing: Add expect-connection calls for all tests and hosts

There are some exceptions (e.g. those that use auto=start or p2pnat).

testing/tests/ikev2/multi-level-ca-strict/pretest.dat

@@ -1,6 +1,8 @@
 moon::ipsec start
 carol::ipsec start
 dave::ipsec start
+moon::expect-connection alice
+moon::expect-connection venus
 carol::expect-connection alice
 carol::expect-connection venus
 carol::ipsec up alice