* CNOS Vlag module is refactored to use persistence connection instead of paramiko.
* Changing interface and port channel modules to persistent connection and adding UT for them.
* Fixing pep8 issues
* Removing trailing new line
* Removing trailing new line
* Removing trailing new line
* Correcting indentation mistake
* Update cnos_vlag.py
* Removing commented examples
They are commented because those configurations are not meant for L2 ports
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