monitor: fix issue with url cached in browser using wrong domain

The problem is explaned here: https://bugs.chromium.org/p/chromium/issues/detail?id=260239

The use of header Vary: Origin dosen't fix the problem on chrome so I disabled the cache
with Pragma "no-cache". This doesn't cause issue because most of monitor files are
modified every minutes and sync happen at least every 5 minutes. So the better solution
is to disable cached.

stack/monitor/buildout.cfg

@@ -87,7 +87,7 @@ md5sum = 1bdb4e05c6be04f4e5766c64467fbcec
 [monitor-httpd-cors]
 <= monitor-template-base
 filename = httpd-cors.cfg.in
-md5sum = 5afad2bb6e088e080e907f1d837effbb
+md5sum = 65cf2c8f5cfffa509ec3fc06b37e7509
 # End templates files
 
 # XXX keep compatibility (with software/ipython_notebook/software.cfg )

stack/monitor/templates/monitor-httpd.conf.in

@@ -54,6 +54,11 @@ AddType application/hal+json .haljson
 SSLEngine   On
 
 Include {{ parameter_dict.get('httpd-cors-config-file') }}
+Header set Vary Origin
+Header set Cache-Control "private, max-age=0, must-revalidate"
+Header set Access-Control-Max-Age "0"
+Header unset ETag
+Header set Pragma "no-cache"
 Header set Access-Control-Allow-Credentials "true"
 Header set Access-Control-Allow-Methods "PROPFIND, PROPPATCH, COPY, MOVE, DELETE, MKCOL, LOCK, UNLOCK, PUT, GETLIB, VERSION-CONTROL, CHECKIN, CHECKOUT, UNCHECKOUT, REPORT, UPDATE, CANCELUPLOAD, HEAD, OPTIONS, GET, POST"
 Header set Access-Control-Allow-Headers "Overwrite, Destination, Content-Type, Depth, User-Agent, X-File-Size, X-Requested-With, If-Modified-Since, X-File-Name, Cache-Control, Authorization"