Bug 7834: order search at the top of acq does nothing

Bug 7834: order search at the top of acq does nothing

Entering a search term for 'title' or 'vendor' at the top search
form in acq (tab 'Orders search') did redirect to the advanced
search form, but didn't start the search.

After applying the patch the search will bring back results immediately
or redirect to the form, when there are no results.

To test:
- Check all searches still work as expected by searching for title,
vendor, order name and invoice number
- Check advanced search still has the search terms prepopulated
- Check searches with and without results are ok

Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>