The value of pwTemplateIgmpMcacUnconstBW specifies the bandwidth
assigned for interface's multicast CAC policy traffic in kilo-bits per
second(kbps).
If the default value of '-1' is set, there is no constraint on
bandwidth allocated at the interface.
If the value of pwTemplateIgmpMcacUnconstBW is set to '0' and if
a multicast CAC policy is assigned on the interface, then
no group (channel) from that policy is allowed on that interface.