Fix a couple simple test failures with updated build.

.travis.yml

@@ -9,7 +9,7 @@ env:
     init: /sbin/init
     run_opts: ""
   - distro: ubuntu1604
-    init: /usr/lib/systemd/systemd
+    init: /lib/systemd/systemd
     run_opts: "--privileged --volume=/sys/fs/cgroup:/sys/fs/cgroup:ro"
   - distro: ubuntu1404
     init: /sbin/init

tests/test.yml

@@ -9,6 +9,10 @@
         - which
       when: ansible_os_family == 'RedHat'
 
+    - name: Update apt cache.
+      apt: update_cache=yes
+      when: ansible_os_family == 'Debian'
+
     - name: Ensure build dependencies are installed (Debian).
       apt: 'name="{{ item }}" state=installed'
       with_items: