Restore module loading

The module loading feature got broken a while ago, so restore it, but
have it a bit more explicit this time around.

Reviewed-by: Stephen Henson <steve@openssl.org>

apps/genpkey.c

@@ -179,6 +179,9 @@ int genpkey_main(int argc, char **argv)
         goto end;
     }
 
+    if (!app_load_modules(NULL))
+        goto end;
+
     out = bio_open_default(outfile, "wb");
     if (out == NULL)
         goto end;