Revert "travis: do not use sudo, but the apt plugin"

This reverts commit 34b55fe3b5.

.travis.yml

@@ -1,26 +1,13 @@
 ---
 dist: bionic
-addons:
-  apt:
-    packages:
-    - devscripts
-    - python
-    - python3
-    - ruby
-    - php-cli
-    - gawk
-    - ksh
-    - zsh
-    - pylint
-    - shellcheck
-    - pkg-config
-    - libdb-dev
-    - libvirt-dev
-    - libexpat-dev
-    - munin-node
-    - libsys-virt-perl
-
 install:
+  - sudo apt-get update
+  - sudo apt-get --no-install-recommends install devscripts python python3 ruby php-cli gawk ksh zsh pylint shellcheck
+  - sudo apt-get --no-install-recommends install pkg-config libdb-dev libvirt-dev libexpat-dev
+  # - Munin/Plugin.pm is in "munin-node" on precise
+  - sudo apt-get --no-install-recommends install munin-node
+  - sudo apt-get --no-install-recommends install libsys-virt-perl
+
   # we use locally installed cpan modules instead of travis' builtin 'homebrew' perl support
   # The homebrew variation does not work for us, since:
   #   * it is built without threading