Fix DeltaFIFO bug that caused the sync delta created by a relist
for object ID X to be dropped if the DeltaFIFO already stored a
Delete delta for X. This caused SharedIndexInformer to miss create
notifications. Also, add unit test to expose the bug.
Kubernetes-commit: 9e4be54895e8c0655408b4766cd78de17b6d5b7c
Nobody uses it; the one or two older users from 1.4/1.5 timeframe
were removed for 1.6. It's also poorly understood and the sole
example is in the testcases, and it's pretty incomplete.
If anyone really wants compression, they can revert this PR.
Kubernetes-commit: a56c8f50cb9b9bfdb92bc5f005a48f8df5afadb9
