r808895 added `ServerTokens OFF` so some modules were
switched from ap_get_server_banner() to
ap_get_server_description() so they would never be empty.
But ap_get_server_description() is documnented as being for local
use only, so it was not really a suitable replacement much less
w/ `ServerTokens OFF` subsequently taken out.
git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1851954 13f79535-47bb-0310-9956-ffa450edef68