The import script as-is isn't guaranteed to run 24+ hours in the
future and therefore unique imports per run are also not guaranteed.
Additionally, the script will be expected to run every few hours
to check for batch errors, exacerbating this problem.

`main.sh` should therefore be able to check if the import it wants
to run has already been run and abort if it has.

- Add support for running the script multiple times a day by aborting
  the import if it's already been completed for the given feeds
- Add support for retrying an import with failed batches
- Add support for retrying an import that didn't complete (eg. database
  disconnect)
- make --batchsize non-optional interally, as non-integer values from
  other parameters were being passed if a batchsize wasn't passed. This
  value still defaults to 10000.

Bug: T344941
Change-Id: If648356e2b62b2c310d9adcef7db361040c29dac