FS-6979 #resolve #comment mod_http_cache: added base-domain config to s3 profiles so mod_http_cache can access self hosted s3 compatible service.

Example configuration:

  <profiles>
    <profile name="s3">
       <!-- Credentials for AWS account. -->
       <aws-s3>
          <!-- 20 character key identifier -->
          <access-key-id><![CDATA[AKIAIOSFODNN7EXAMPLE]]></access-key-id>
          <!-- 40 character secret -->
          <secret-access-key><![CDATA[wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY]]></secret-access-key>
          <base-domain><![CDATA[example.com]]></base-domain>
       </aws-s3>
       <!-- Domains that this profile applies to -->
       <domains>
          <domain name="bucket.example.com"/>
          <domain name="bucket2.example.com"/>
       </domains>
    </profile>
  </profiles>