Fix apt module to be able to install package by giving just a provides and not the full name

The apt module check if a packag eis valid by loking in the cache, checking only for
full name, while it should also check that the name is not just provided.
Fix https://github.com/ansible/ansible/issues/5177
Merge pull request #5182 from mscherer/fix_5177

Fix apt module to be able to install package by giving just a provides a...