Cache constructor doesn't properly set prefix from default bin

We enabled cacherouter across a multisite setup of drupal where each site requires it's own cache. So each site had it's own cache we set the prefix in the default bin:

$conf['cacherouter'] = array(
  'default' => array(
    'engine' => 'memcache',
    'server' => array('localhost:11211'),
    'shared' => TRUE,
    'prefix' => $cache_prefix,
  ),
);

We noticed errors with the output on each site - in particular the wrong theme being used and upon further investigation noticed that the Cache class wasn't setting prefix from the default bin if a specific bin wasn't explicitly specified.

This patch fixes this problem by reverting to the prefix in default bin if it is set. Patch was made against HEAD.

This appears to be have been fixed in the large patch in http://drupal.org/node/262830

This patch was developed by IDG Australia