If kube-apiservers run at a different version (during upgrades) and
each has different opinion on what the `extension-apiserver-authentication`
config map should look like, they would start dueling with config map
writes.
This commit removes handling of the update events of the target CM
in order to reduce the amount of such dueling to once a minute, as
the controller is guaranteed to run at least once a minute anyway.
The idea is that a cluster state with two different versions of
kube-apiserver should never be permanent, and so a reduced amount of
dueling for that period is tolerable.
This commit includes all the changes needed for APIServer. Instead of modifying the existing signatures for the methods which either generate or return stopChannel, we generate a context from the channel and use the generated context to be passed to the controllers which are started in APIServer. This ensures we don't have to touch APIServer dependencies.
