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/mobike/pretest.dat

@@ -4,6 +4,5 @@ sun::iptables-restore < /etc/iptables.rules
 sun::ip route add 10.1.0.0/16 via PH_IP_MOON
 alice::ipsec start
 sun::ipsec start
-alice::sleep 2
+alice::expect-connection mobike
 alice::ipsec up mobike
-alice::sleep 1