The value of vRtrPimNgGenEnableMdtSpt specifies whether or not
Shortest Path Tree(SPT) switchover is enabled for the default Multicast
Data Tunnel(MDT). If set to 'true' then SPT switchover is enabled and
if set to 'false' SPT switchover is disabled. Additionally, whenever
we change the value of 'vRtrPimNgGenEnableMdtSpt', the PIM instance
must reset all MDTs and re-initiate setup.