perl: Remove bashism from perl-tests.inc

The perl-tests.inc file where using the constructs:

 cp {a,b} to/

but this is not supported in every shell so we cannot use it. This
patch fixes it.

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>