testing: Remove nearly all sleep calls from pretest and posttest scripts

By consistently using the `expect-connection` helper we can avoid pretty
much all previously needed calls to sleep.

testing/tests/ikev1/multi-level-ca-cr-init/pretest.dat

@@ -1,6 +1,7 @@
 carol::ipsec start
 dave::ipsec start
 moon::ipsec start
-moon::sleep 2
+moon::expect-connection alice
+moon::expect-connection venus
 moon::ipsec up alice
 moon::ipsec up venus