Fix insufficient results during filtering

[kishorenc]

Very similar in nature to #344

I've discussed this fix with @dyashuni before and this has been tested on a number of datasets.

[dyashuni]

Thank you, @kishorenc

Idea of the fix:
if filter is enabled (!isIdAllowed is false) we don’t care about performance and we should check
top_candidates.size() == ef

if filter is disabled (!isIdAllowed is true) we should have the same behaviour as without filter
top_candidates.size() == ef || !has_deletions

[dyashuni]

Thank you, @kishorenc