testing: Explicitly deliver all test results as text/plain

testing/hosts/winnetou/etc/apache2/conf-enabled/testresults-as-text.conf

@@ -1 +1,4 @@
-AddType text/plain .iptables .log .sql
+AddType text/plain .conf .log .sql .users
+AddType text/plain .secrets .listall .statusall
+AddType text/plain .conns .certs .sas .pools .authorities .stats
+AddType text/plain .policy .state .route .iptables .iptables-save