Marking the pods not ready on a node requires looping over them and
updating each pod's status one at a time. This is performed serially,
and can take a while if we're processing each node serially as well.
Since the time is spent waiting on io, there's an opportunity to go
faster by processing multiple nodes concurrently. This change modifies
the loop to process nodes in parallel, using the same number of workers
as doNodeProcessingPassWorker.
This change also introduces histogram metrics to better observe
monitorNodeHealth.
Prepatory work fpr removing cloud provider dependency from node
controller running in Kube Controller Manager. Splitting the node
controller into its two major pieces life-cycle and CIDR/IP
management. Both pieces currently need the the cloud system to do their work.
Removing lifecycles dependency on cloud will be fixed ina followup PR.
Moved node scheduler code to live with node lifecycle controller.
Got the IPAM/Lifecycle split completed. Still need to rename pieces.
Made changes to the utils and tests so they would be in the appropriate
package.
Moved the node based ipam code to nodeipam.
Made the relevant tests pass.
Moved common node controller util code to nodeutil.
Removed unneeded pod informer sync from node ipam controller.
Fixed linter issues.
Factored in feedback from @gmarek.
Factored in feedback from @mtaufen.
Undoing unneeded change.
