(SLTS) - Possible failure during deletion of metadata keys can cause version mismatch in next attempt.

[sachin-j-joshi]

Problem description
Currently table store has a severe limitation that it can not update and delete keys in the same transaction.
The current work around for this problem is implemented in two steps in TableBasedMetadataStore.writeAll method.
It involves first marking the keys as deleted by updating in first transaction and immediately deleting them.
This works fine as long as both steps succeed, however when second step fails then the whole transaction is aborted. Leaving behind update keys with new version which do not match expected version when new transaction with same keys is reattempted.

Problem location
TableBasedMetadataStore.writeAll

Suggestions for an improvement
Do not fail transaction if keys are successfully marked as deleted even though deleting them failed.