Make ews django app robust against buildbot downtime. When ews django app starts, it fetches builder_name_to_id_mapping from Buildbot server. It fetches it only once. If Buildbot server was down at that moment or there was any network issue, that mapping isn't fetched. This mapping is used to decide which patches to send to Commit-Queue (by fetching list of pending_and_inprogress_builds on commit-queue). Although failure to fetch this mapping doesn't cause any functionality issue, since the logic is able to work without this mapping as well, it becomes little inefficient and logs have error messages like: "Invalid builder: Commit-Queue".

We should re-fetch this mapping when required to make ews django app more robust against Buildbot downtime or network issues.