openssl: unbreak PKCS12 support

Regression introduced in ce362e8eb9 (7.31.0)

Bug: http://curl.haxx.se/bug/view.cgi?id=1371
Reported-by: Dmitry

lib/vtls/openssl.c

@@ -538,6 +538,7 @@ int cert_stuff(struct connectdata *conn,
 
       if(!cert_done)
         return 0; /* failure! */
+      break;
 #else
       failf(data, "file type P12 for certificate not supported");
       return 0;