run-travis: disable clisp test for now

The travis build fails with

```
[package cl-gtk2-init].....

*** - handle_fault error2 ! address = 0xccca23ea8 not in [0x333c98000,0x33443f6f8) !

SIGSEGV cannot be cured. Fault address = 0xccca23ea8.

GC count: 372

Space collected by GC: 644632400

Run time: 13 780904

Real time: 14 585288

GC time: 3 40526

Permanently allocated: 164640 bytes.

Currently in use: 13762304 bytes.

Free space: 2999202 bytes.

Segmentation fault
```