In the httpd module, serveraliases defaults to undef, which evaluates to
nil in ERB templates. Ensure the template checks for nil values so that
the ServerAlias line is only included if there is a server alias.
Also correct the variable usage in the index.html.erb template.
Change-Id: Ibde097b7dd407884336154a318ec4c5661fda03c
63153c941e