Automatic merge from submit-queue
Add node problem detector as an addon pod.
```release-note
Introduce a new add-on pod NodeProblemDetector.
NodeProblemDetector is a DaemonSet running on each node, monitoring node health and reporting
node problems as NodeCondition and Event. Currently it already supports kernel log monitoring, and
will support more problem detection in the future. It is enabled by default on gce now.
```
This PR enables NodeProblemDetector as an add-on pod.
/cc @mikedanese @kubernetes/sig-node
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Allow the gcr.io/google_containers registry to be overridden
regionally by just blasting a new KUBE_ADDON_REGISTRY out. Instead of
adding every addon to Salt and asking all of the other consumers
(Trusty, Juju, Mesos, etc) to change, just script the sed ourselves.
This is probably the 9th grossest thing I've ever done, but it works
well, and it works quickly. I kind of wish it didn't.
* In kube-up.sh, create a staging bucket with a location nearest the
zone being created. If new variable RELEASE_REGION_FALLBACK is set
(default false), create multiple buckets and stage to fallback
URLs. (In open source, this path is primarily for testing.)
* In configure-vm.sh, split the URL env variables by comma (if any
extra are present) and retry on the fallback URLs. Also factor the
hash checking into this path rather than outside, since a corrupt
release in a particular geo can be retried in a different geo.
* Remove the local already-staged .tar.gz checks. They've caused
several issues along the way, and with this code path become virtually
unmaintainable. (I could add a sentinel for each bucket it's possibly
staged to, but ew.)
Implement a flag that defines the frequency at which a node's out of
disk condition can change its status. Use this flag to suspend out of
disk status changes in the time period specified by the flag, after
the status is changed once.
Set the flag to 0 in e2e tests so that we can predictably test out of
disk node condition.
Also, use util.Clock interface for all time related functionality in
the kubelet. Calling time functions in unversioned package or time
package such as unversioned.Now() or time.Now() makes it really hard
to test such code. It also makes the tests flaky and sometimes
unnecessarily slow due to time.Sleep() calls used to simulate the
time elapsed. So use util.Clock interface instead which can be faked
in the tests.