fix apache::vhost concat test breakage

We do not need to verify the contents of the file that apache::vhost
(via concat) generates, so just skip it.

Closes-Bug: #1392499
(cherry picked from commit c38e7a619b0cbde3c381d15bbceb4a06e2b048bb)

Change-Id: Ic765fd12e1fe69e35cc021457769b684b5897178