Add backoff to avoid infinite compact_mem_table fails

[Fullstop000]

If compact_mem_table fails, the immutable memtable will be still there. And we re-schedule compaction after a compaction which means compact_mem_table will be called infinitely. To fix this, we can introduce a backoff to prevent the infinite compaction loop.
If compaction fails hits the backoff limit, prevent all writing requests to the wickdb could be a good choice.