testing: add a testcase for plain XAuth RADIUS authentication

testing/tests/ikev1/xauth-rsa-radius/hosts/carol/etc/strongswan.conf

@@ -0,0 +1,9 @@
+# /etc/strongswan.conf - strongSwan configuration file
+
+charon {
+  load = sha1 sha2 md5 aes des hmac pem pkcs1 x509 revocation gmp random nonce curl xauth-generic kernel-netlink socket-default updown stroke
+}
+
+libstrongswan {
+  dh_exponent_ansi_x9_42 = no
+}