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/tnc/tnccs-20-hcd-eap/pretest.dat

@@ -11,7 +11,7 @@ alice::ipsec start
 moon::ipsec start
 carol::ipsec start
 dave::ipsec start
-dave::sleep 1
+carol::expect-connection home
 carol::ipsec up home
+dave::expect-connection home
 dave::ipsec up home
-dave::sleep 1