Bug 20906: Fix translatable-templates.t

Bug 20906: Fix translatable-templates.t

From Jenkins:
koha_1       | #   Failed test 'staff_prog templates are translatable'
koha_1       | #   at xt/author/translatable-templates.t line 87.
koha_1       | # Can't locate TmplTokenizer.pm in @INC (you may need to install the TmplTokenizer module) (@INC contains: /kohadevbox/koha /etc/perl /usr/local/lib/x86_64-linux-gnu/perl/5.24.1 /usr/local/share/perl/5.24.1 /usr/lib/x86_64-linux-gnu/perl5/5.24 /usr/share/perl5 /usr/lib/x86_64-linux-gnu/perl/5.24 /usr/share/perl/5.24 /usr/local/lib/site_perl /usr/lib/x86_64-linux-gnu/perl-base) at ./tmpl_process3.pl line 20.

On Stretch, '.' is not longer added to @INC, see bug 17717 for more info

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>