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/ikev2/ip-pool-db/pretest.dat

@@ -7,10 +7,10 @@ moon::ipsec pool --addattr nbns --server PH_IP_VENUS 2> /dev/null
 moon::iptables-restore < /etc/iptables.rules
 carol::iptables-restore < /etc/iptables.rules
 dave::iptables-restore < /etc/iptables.rules
+moon::ipsec start
 carol::ipsec start
 dave::ipsec start
-moon::ipsec start
-carol::sleep 2
+carol::expect-connection home
 carol::ipsec up home
+dave::expect-connection home
 dave::ipsec up home
-carol::sleep 1