Bug 13728: koha-translate -l -a shows po files instead of language codes

Bug 13728: koha-translate -l -a shows po files instead of language codes

This patch corrects the call to 'basename' inside the script so it correctly
shows the language code when asked to list the available languages.

To test:
- On a packages install, run:
  $ koha-translate --list --available
=> FAIL: It shows:
am-Ethi-opac-bootstrap.po
ar-Arab-opac-bootstrap.po
az-AZ-opac-bootstrap.po
be-BY-opac-bootstrap.po
ben-opac-bootstrap.po
...

- Apply the patch
- Copy the patched debian/scripts/koha-translate script to your packages setup.
- Run:
  $ koha-translate --list --available
=> SUCCESS: It shows:
am-Ethi
ar-Arab
az-AZ
be-BY
ben
...

- Sign off :-D

Sponsored-by: Universidad Nacional de Cordoba
Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>
(cherry picked from commit 6b26f8858e5069a2fae21fb28692a8eeb37fa0a8)
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>