Simplify editor-linter
Simplify editor-linter

* Moving `catch` up the promise chain removes one logical branch. there doesn't
  appear to be any functional difference between deleting the previous results
  and overwriting them with an empty array. It's what would happen if there were
  no errors.
* replacing the `progress` getter/setter with `_promiseLock` makes it clear
  that this is a private function and simplifies the process of setting and
  releasing the lock

Arcanemagus/linter,steelbrain/linter,AsaAyers/linter,DanPurdy/linter,josa42/Linter,levity/linter,atom-community/linter,AtomLinter/Linter,UltCombo/linter,shawninder/linter,elkeis/linter,iam4x/linter,JohnMurga/linter,kaeluka/linter,simurai/linter-plus,e-jigsaw/Linter,blakeembrey/linter,mdgriffith/linter