testing: add a testcase for plain XAuth RADIUS authentication

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

@@ -0,0 +1,11 @@
+# /etc/strongswan.conf - strongSwan configuration file
+
+charon {
+  load = curl aes des sha1 sha2 md5 pem pkcs1 gmp random nonce x509 revocation hmac stroke kernel-netlink socket-default fips-prf eap-radius updown
+  plugins {
+    eap-radius {
+      secret = gv6URkSs
+      server = PH_IP_ALICE
+    }
+  }
+}