[ScaleUP and ScaleOUT]Clean old CNI configuration file before install new CNI for bridge, flannel and mizar and clean interface cni0 when shutdown scaleup cluster with bridge and flannel

[q131172019]

What type of PR is this? /kind cleanup

What this PR does / why we need it: This PR is to give better development experience when switch different cniplugin.

1. Clean old cni configuration files in the directories /etc/cni/net.d and /opt/cni/bin before new cni is installed and started with bridge, flannel or mizar
2. Cleaning interface and ip link for cni0 to fix the conflict of cni0 associating with different ip addresses when switch different cniplugin between bridge and flannel to start scale-up cluster

By the way, this PR makes improvement to keep the consistency of local variables and global variables in hack/arktos-cni.rc

Tests have been done in the following 3 AWS environments:

Scale-up environment Ubuntu 18.04 (master + 3 workers)

• default (cniplugin=bridge)
• cniplugin=flannel
• cniplugin=mizar

Scale-up environment Ubuntu 20.04 (master + 3 workers)

• default (cniplugin=bridge)
• cniplugin=flannel
• cniplugin=mizar

Scale-out 2x2 environment Ubuntu 20.04 (2 TPs X 2 RPs and each RP with 1 worker)

• default (cniplugin=flannel)
• cniplugin=mizar

Which issue(s) this PR fixes: Issue 1399 Issue 1348

Special notes for your reviewer: N/A

Does this PR introduce a user-facing change?: N/A

[zmn223]

/lgtm

[zmn223]

/approve

[centaurus-cloud-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Sindica, sonyafenge, zmn223

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