Add Test case to verify Spanning Tree (RPVST) state

[vitthalmagadum]

Test Criteria: Ignore anything under the Topology= NoStp section. For all other Topologies returned, number of changes should be less than ExpectedNoOfChange indicating a stable topology

Sample output:

DLF#show spanning-tree topology status detail Topology: NoStp Mapped Vlans: 1501-1506 Cpu: forwarding (1 changes, last 179 days, 6:58:55 ago) Ethernet49/1: forwarding (1 changes, last 179 days, 6:58:42 ago) Topology: Vl1500 Mapped Vlans: 1500 Cpu: forwarding (1 changes, last 179 days, 6:58:55 ago) Port-Channel100: forwarding (1 changes, last 179 days, 6:58:55 ago) Vxlan1: forwarding (1 changes, last 179 days, 6:58:55 ago)

Topology: Vl1999 Mapped Vlans: 1999 Cpu: forwarding (1 changes, last 179 days, 6:58:42 ago) Port-Channel100: forwarding (1 changes, last 179 days, 6:58:42 ago) Vxlan1: forwarding (1 changes, last 179 days, 6:58:42 ago)