testing: Load kdf plugin in all scenarios that require it

Once we use plugin-provided prf+() these won't work otherwise.

testing/tests/ikev2/strong-keys-certs/hosts/carol/etc/strongswan.conf

@@ -5,5 +5,5 @@ swanctl {
 }
 
 charon-systemd {
-  load = random nonce aes sha1 sha2 md5 pem pkcs1 curve25519 gmp x509 curl revocation hmac vici kernel-netlink socket-default updown
+  load = random nonce aes sha1 sha2 md5 pem pkcs1 curve25519 gmp x509 curl revocation hmac kdf vici kernel-netlink socket-default updown
 }

testing/tests/ikev2/strong-keys-certs/hosts/dave/etc/strongswan.conf

@@ -5,5 +5,5 @@ swanctl {
 }
 
 charon-systemd {
-  load = random drbg nonce aes des md5 sha1 sha2 sha3 chapoly pem pkcs1 pkcs8 curve25519 gmp newhope mgf1 ntru x509 curl revocation hmac xcbc ctr ccm gcm vici kernel-netlink socket-default updown
+  load = random drbg nonce aes des md5 sha1 sha2 sha3 chapoly pem pkcs1 pkcs8 curve25519 gmp newhope mgf1 ntru x509 curl revocation hmac kdf xcbc ctr ccm gcm vici kernel-netlink socket-default updown
 }

testing/tests/ikev2/strong-keys-certs/hosts/moon/etc/strongswan.conf

@@ -5,5 +5,5 @@ swanctl {
 }
 
 charon-systemd {
-  load = random nonce aes sha1 sha2 md5 pem pkcs1 curve25519 gmp x509 curl revocation hmac vici kernel-netlink socket-default updown
+  load = random nonce aes sha1 sha2 md5 pem pkcs1 curve25519 gmp x509 curl revocation hmac kdf vici kernel-netlink socket-default updown
 }