testing: Adapt tests to retransmission settings and reduce DPD delay/timeout

testing/tests/tnc/tnccs-20-pts-no-ecc/hosts/dave/etc/strongswan.conf

@@ -3,6 +3,8 @@
 charon {
   load = aes md5 sha1 sha2 hmac gmp pem pkcs1 random nonce x509 curl revocation stroke kernel-netlink socket-default eap-identity eap-md5 eap-ttls eap-tnc tnc-imc tnc-tnccs tnccs-20 updown
 
+  retransmit_timeout =
+
   multiple_authentication = no
 
   plugins {