travis-ci: don't install default addon packages for the 32 bit Linux build

The 32 bit Linux build job compiles Git and runs the test suite in a
Docker container, while the additional packages (apache2, git-svn,
language-pack-is) are installed on the host, therefore don't have
any effect and are unnecessary.

Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
Acked-by: Lars Schneider <larsxschneider@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

.travis.yml

@@ -42,6 +42,7 @@ matrix:
     - env: jobname=Linux32
       os: linux
       compiler:
+      addons:
       services:
         - docker
       before_install: