I have a Nexus 7009 with 2 Supervisors SUP2E and NX-OS 6.1(4).
After a system switchover between Supervisor multicast traffic is not forwarded for about 50 seconds and the output of 'show ip mroute' shows pending entries:
Nexus7K# sh ip mroute vrf MAIN
IP Multicast Routing Table for VRF "MAIN"
(initializing - suppressing notifications & MFDM updates, time-left: 00:00:42)
(*, 184.108.40.206/4) [pending], uptime: 00:00:51, pim
Incoming interface: Null, RPF nbr: 0.0.0.0
Outgoing interface list: (count: 0)
(10.250.69.100/32, 220.127.116.11/32) [pending], uptime: 00:00:37, igmp
Outgoing interface list: (count: 1)
Vlan520, uptime: 00:00:37, igmp
(10.69.20.100/32, 18.104.22.168/32) [pending], uptime: 00:00:15, ip
Incoming interface: Vlan520, RPF nbr: 10.69.20.100
Only after the 'time-left' expires the multicast traffic is forwarded again.
ip routing multicast holddown 0
This will reduce the Multicast routing update between 2 SUPs