BUG/MEDIUM: ssl: does not try to free a DH in a ckch

ssl_sock_load_dh_params() should not free the DH * of a ckch, or the
ckch won't be usable during the next call.
diff --git a/src/ssl_sock.c b/src/ssl_sock.c
index ceadc9b..0eaf2eb 100644
--- a/src/ssl_sock.c
+++ b/src/ssl_sock.c
@@ -2858,10 +2858,8 @@
 	int ret = -1;
 	DH *dh = NULL;
 
-	if (ckch)
+	if (ckch && ckch->dh) {
 		dh = ckch->dh;
-
-	if (dh) {
 		ret = 1;
 		SSL_CTX_set_tmp_dh(ctx, dh);
 
@@ -2897,9 +2895,6 @@
 	}
 
 end:
-	if (dh)
-		DH_free(dh);
-
 	return ret;
 }
 #endif