[#729] Handle languages in URLs when updating page view tracking summary

Page view tracking was failing when a language was selected:

1. Put `ckan.tracking_enabled = true` in your ini file
2. Run CKAN, visit a page with a language e.g. `/en/dataset/annakarenina`
3. Run `paster tracking update`. If you look in your db, in the
   `tracking_summary` table there'll be a row with `package_id`
   `~~not~found~~`.
4. Run `paster tracking export tracking.csv`, the exported CSV file will
   say 0 views.

If you visit the page without the language in the URL e.g.
`/dataset/annakarenina` then run the export command again, the view does
get counted.

This commit fixes the SQL used by the `paster tracking update/export`
command to handle URLs with or without languages at the start.

Fixes #729