RT-1.36: AIGP feature support test

[ksgireesha]

Implement code for RT-1.36: AIGP feature support test

This README covers the following requirements:

• ISIS – Existing configuration w/ sub-interface in default VRF
• ISIS – Existing configuration w/ sub-interface in non-default VRF
• iBGP & eBGP – Existing configuration w/ interface in default VRF
• iBGP & eBGP – Existing configuration w/ sub-interface in default VRF
• iBGP & eBGP – Existing configuration w/ sub-interface in non-default VRF
• iBGP & eBGP – IPv4 and IPv6 addressing in non-default VRF
• iBGP & eBGP – Separate ASN in non-default VRF
• iBGP & eBGP – Route reflector capabilities in default VRF
• iBGP & eBGP – Route reflector capabilities in non-default VRF
• iBGP & eBGP – Set next hop in default VRF
• iBGP & eBGP – Set next hop in non-default VRF
• iBGP & eBGP – Allow own as in default VRF
• iBGP & eBGP – Advertise peer AS in default VRF
• iBGP & eBGP – Advertise AIGP in non-default VRF
• iBGP & eBGP – Set AIGP on import/export in non-default VRF