Fix push handling to be robust to missing server files.

W/o this the server crashes if you add a new server to skiapush.conf.

BUG=skia:
TBR=rmistry

Review URL: https://codereview.chromium.org/814253002
Revert of Refactored Ingestion and tiletool (patchset #9 id:150001 of https://codereview.chromium.org/805803004/)

Reason for revert:
Repeated restart takes too long. Needs to be fixed while other changes are added.

Original issue's description:
> This changes how ingestion fetches data and extends the tiletool. In particular:
>
> - Ingester now loads result files relative to the latest commit.
>
> - What is ingested is configured by specifying a minimum number of commits we want and how far back (days) we want to cover.
>
> - Downloaded files are cached and not ingested anymore if
>   they have been ingested before.
>
> - The tiletool works for perf as well as gold data.
>
> BUG=skia:2930
>
> Committed: https://skia.googlesource.com/buildbot/+/343aa3efbd8513863dd8cd3386bd050b87390b05

TBR=jcgregorio@google.com
NOTREECHECKS=true
NOTRY=true
BUG=skia:2930

Review URL: https://codereview.chromium.org/808553010
Revert of Adjusted flags in ingest_init (patchset #1 id:1 of https://codereview.chromium.org/813803003/)

Reason for revert:
Need to fix changed ingestion before we change this.

Original issue's description:
> Adjusted flags in ingest_init
>
> BUG=skia:
> TBR=jcgregorio
>
> Committed: https://skia.googlesource.com/buildbot/+/55747702b8caaa534ce57d729a5b652db28cb104

TBR=jcgregorio@google.com
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review URL: https://codereview.chromium.org/816943003