Investigate and fix any unhandled error paths when removing wal files

[praveen-influx]

As part of the snapshotting process, currently wal files are removed leaving behind N wal files. Currently anything other than Generic are considered to be ok to move on. If it is a Generic error, there is a retry mechanism to keep trying until it is successful. It is not clear just on the surface what error types are mapped to Generic by object store. If there are intermittent connection failures do they end up as Generic error, if they do not then that needs to be handled separately.