Fix partials being represented as misses (in some cases)

[Max Chadwick]

We can still have a partial hit even without any containers that need additional processing. This can happen here

$sessionInfo = Enterprise_PageCache_Model_Cache::getCacheInstance()->load($this->getSessionInfoCacheId());

if ($sessionInfo) {
    // Handle session info 
} else {
    // This will be a partial. There don't need to be containers for this to happen
    $isProcessed = false;
}

Probably a better approach is to check if the request is being handled by pagecache/request/process.

[Max Chadwick]

Fixed by f53ffa4