Poseidon behave like default scheduler

[shivramsrivastava]

This PR is to make Poseidon behave like default scheduler.

Setting the flag --defaultBehaviour=true will make 'Poseidon' behave like default-scheduler. By default it will be set to false.

Note: This behaviour will not schedule any 'kube-system' pods and it will not process any updates, delete request from 'kube-system' pods.

Scenario: First bring up the cluster using default-scheduler and then remove the default-scheduler before starting 'Poseidon' as default scheduler.

Removing default-scheduler: In the master node, move the file kube-scheduler.manifest from /etc/kubernetes/manifests path. Check if the kube-scheduler is not running, after the above step.

Running Poseidon: As a standalone process it can run with the flag mentioned above. But if you need to run 'Poseidon' as deployment, first bring up the cluster and then bring up the 'Poseidon' and 'Firmament' deployments and then remove the default scheduler. This is once the 'Poseidon' and 'Firmament' is scheduled to run on node by default-scheduler then remove the default-scheduler using the step mentioned above.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: shivramsrivastava

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Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/kubernetes-sigs/poseidon/blob/master/OWNERS)~~ [shivramsrivastava] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[deepak-vij]

/ok-to-test

[deepak-vij]

/lgtm