testing: Use expect-connection in swanctl scenarios

Only in net2net-start do we have to use `sleep` to ensure the SA is
up when the tests are running.

testing/tests/swanctl/ip-pool/pretest.dat

@@ -4,6 +4,8 @@ dave::iptables-restore < /etc/iptables.rules
 moon::service charon start 2> /dev/null
 carol::service charon start 2> /dev/null
 dave::service charon start 2> /dev/null
-moon::sleep 1
+moon::expect-connection rw
+carol::expect-connection home
 carol::swanctl --initiate --child home 2> /dev/null
+dave::expect-connection home
 dave::swanctl --initiate --child home 2> /dev/null