Problem: The Cirrus Search dump script is not resilient enough to failures (elasticsearch restarts), causing cirrus dumps for some wikis to be missing for some weeks.
Solution probably involves stopping use of elastic "srcoll" API
AC:
* Make the dump script more resilient, so that cirrus dumps no longer fail when restarting elasticsearch
***
original log below, and additional logs in comments.
For this week's run:
```
<13>Oct 7 08:09:36 dumpsgen: extensions/CirrusSearch/maintenance/DumpIndex.php failed for /mnt/dumpsdata/otherdumps/cirrussearch/20201005/eswiki-20201005-cirrussearch-general.json.gz
<13>Oct 7 08:09:37 dumpsgen: extensions/CirrusSearch/maintenance/DumpIndex.php failed for /mnt/dumpsdata/otherdumps/cirrussearch/20201005/eswikibooks-20201005-cirrussearch-content.json.gz
<13>Oct 7 08:09:37 dumpsgen: extensions/CirrusSearch/maintenance/DumpIndex.php failed for /mnt/dumpsdata/otherdumps/cirrussearch/20201005/eswikibooks-20201005-cirrussearch-general.json.gz
```