With the old strategy, it was possible for an init container to end up
running without some of its CPUs being exclusive if it requested more
guaranteed CPUs than the sum of all guaranteed CPUs requested by app
containers. Unfortunately, this case was not caught by our unit tests
because they didn't validate the state of the defaultCPUSet to ensure
there was no overlap with CPUs assigned to containers. This patch
updates the strategy to reuse the CPUs assigned to init containers
across into app containers, while avoiding this edge case. It also
updates the unit tests to now catch this type of error in the future.
- As discussed in reviews and other public channels,
this abstraction is used to represent numa nodes, not sockets.
- There is nothing inherently related to sockets in this package anyway.
Test the cases where the number of CPUs available in the system is
smaller or larger than the number of CPUs known in the state, which
should lead to a panic. This covers both CPU onlining and offlining. The
case where the number of CPUs matches is already covered by the
"non-corrupted state" test.
