fix opencv_run_all_tests_unix.sh script:

use `bash` shell instead of `sh`, since on Ubuntu `sh` by default is `dash`,
and `dash` doesn't support `PIPESTATUS` feature used in this sctipt

cmake/templates/opencv_run_all_tests_unix.sh.in

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 
 # Text style