Clean-up backend package test

[dstpierre]

Since the merge of #88 the make alltest is now failing due to the way the search package seems to have conflict opening the search index file while tests are running in parallel / concurrently.

Bottom line is that the Setup function of the backend package should not instantiate the search.Search struct by calling its New function.

Not extremely clear what should be the right course of action from here. I believe the tests and the entire dependency will need some more thinking to prevent that kind of issues.