Port channel chnages

[rahul-1475]

Fixed issues:

• Add property “static” (configurable)
• fallback (configurable) default false.
• fast-rate (configurable) default false.
• min-links (configurable) possible values 1-32 default 1.
• description (configurable) default false.
• graceful_shutdown_mode (configurable) default ENABLE
• Add member vlan to portchannel. (Currently only Ethernets can be PortChannel members)
• Assign/Remove IP to portchannel. (IP validation to be performed on UI and backend)
• Tests for config verification of above parameters.

Unresolved issues:

UI - Respective Display and Config Operations need to be supported on UI. The "name" field on the UI is respective to "static" field above in the backend. On the UI "name" field can be renamed to "protocol name" and if value of "static" is true the "protocol name" should be "lacp" else "protocol name" should be "none". This issue will be fixed by @vivek-metricdust

[kamalkrbh]

@rahul-1475, Use black formatter.