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/pfkey/compress/pretest.dat

@@ -2,5 +2,5 @@ carol::iptables-restore < /etc/iptables.rules
 moon::iptables-restore < /etc/iptables.rules
 carol::ipsec start
 moon::ipsec start
-carol::sleep 2
+carol::expect-connection home
 carol::ipsec up home