check: silence ServerName warnings with MPM DSOs

When using shared MPMs, `httpd -V` will perform a full configuration
check, which emits warnings when there is no defined ServerName.
Unfortunately the test suite does a -V check for every test section,
spamming the output with noise.

Work around this by just uncommenting the example ServerName in the test
config.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/trunk-test-integration@1782066 13f79535-47bb-0310-9956-ffa450edef68