util.promise: Remove some redundant checks, add tests confirming redundancy This lines don't appear to do anything useful, and all tests pass when they are removed. Discovered via mutation testing. I added extra tests to exercise this code, because I wasn't certain that there were no side-effects caused by removal. Everything appears to be fine, thanks to the "pending" check at the start of promise_settle().

return {
  _all = {
  },
  default = {
    ["exclude-tags"] = "mod_bosh,storage,SLOW";
  };
  bosh = {
    tags = "mod_bosh";
  };
  storage = {
    tags = "storage";
  };
}