internet connectivity not always read correctly

Currently, scope-aggregator uses a QueryMetadata object initialized at Query constructor time to get the internet connectivity status, and experience shows this object is sometimes stale and the results are not reliable.

Object initialization:
http://bazaar.launchpad.net/~scope-aggregator/scope-aggregator/vivid-trunk/view/head:/src/query.cpp#L59
Object use:
http://bazaar.launchpad.net/~scope-aggregator/scope-aggregator/vivid-trunk/view/head:/src/utils.cpp#L1213

For example, sometimes using this object the QueryMetadata::ConnectivityStatus is Unknown or not set.

I find when getting the QueryMetatdata fresh every time with search_metadata() I get much better results (Connected or Disconnected).

So, scope-agg should always use search_metadata().

This should fix intermittent issues with agg scopes providing help messages on No Internet condition (like News scope https://bugs.launchpad.net/news-scope/+bug/1476160).