fix: lookup of meta data by alias

[sgratzl]

closes the root cause of cmu-delphi/www-covidcast#983

Prerequisites:

• Unless it is a documentation hotfix it should be merged against the dev branch
• Branch is up-to-date with the branch to be merged with, i.e. dev
• Build is successful
• Code is cleaned up and formatted

Summary

fixes the generation of the new meta data which was buggy for the db alias in the meta lookup

i.e. the reason why chng wasn't part of https://api.covidcast.cmu.edu/epidata/covidcast/meta

[krivard]

👍