Rework GC transaction retries
- Limit to 2 rather than 100 attempts for each key.
- Try to GC next key after max attempts failed rather than stopping GC completely.
I also want to add some counters to monitor the situation but I ran out of time today. This can go in and I'll add counters in a follow up.
This addresses https://new-sentry.gitlab.net/organizations/gitlab/issues/279758/?project=11: Failed to GC data in Redis: failed to execute Redis transaction 100 times
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Relates to #386 (closed).
Edited by Mikhail Mazurskiy