fix scan timeframe with use_terms_query

[rschirin]

Description

Following issue Yelp/elastalert#3041 and PR Yelp/elastalert#3141, when a rule has [scan_entire_timeframe: true] and [use_terms_query: true or use_count_query: true], the timeframe (i.e. 5 days) is evaluated correctly just at first run; from the second one, the timeframe will be set accordly to run_every value (i.e. 5 minutes).
This change only affects rules with option use_count_query or use_term_query.

Checklist

• I have reviewed the contributing guidelines.
• I have included unit tests for my changes or additions.
• I have successfully run make test-docker with my changes.
• I have manually tested all relevant modes of the change in this PR.
• I have updated the documentation.
• I have updated the changelog.

Questions or Comments