Add test case to verify the BGP route origin.

[vitthalmagadum]

verifying BGP route origin:

IGP (i):

This indicates that the route was learned from an Interior Gateway Protocol (IGP) within the originating autonomous system (AS).

EGP (e):

This signifies that the route was learned from the Exterior Gateway Protocol (EGP), an older protocol that predates BGP.

INCOMPLETE (?):

This value indicates that the route's origin is unknown or that it was learned in a way that doesn’t fit the IGP or EGP categories.