page caching ignores presence of hst:cachable property on mount

According to the Regression test plan page caching should be disabled if a mount has the property hst:cachable set to false while on a parent node it is set to true.

Steps to reproduce (using cargo.run on gogreen-enterprise)
Login to console
On node hst:hosts set property hst:cachable = true
On node hst:mount (child of hst:hosts) set property hst:cachable = false

Access localhost:8080/site/sitemap twice and inspect the hippo-site.log.
Expected:
The PageCachingValve does NOT cache page rendering
Actual
The PageCachingValve caches page rendering

Logging in hippo-site.log after 2nd page request:

15.04.2015 11:46:28 INFO  [org.hippoecm.hst.core.container.DiagnosticReportingValve.logDiagnosticSummary():45] Diagnostic Summary:
- HstDelegateeFilterBean (6ms): {request=Request{ method='GET', scheme='http', host='localhost:8080', requestURI='/site/sitemap', queryString='null'}}
  |- Host and Mount Matching (0ms): {}
  |- Sitemap Matching (0ms): {}
  `- Pipeline processing (6ms): {pipeline=null}
     |- Targeting update valve (4ms): {}
     `- PageCachingValve (1ms): {}