The value of tmnxSubMcacPlcyUnconstrainedBW specifies the bandwidth
assigned to this subscriber MCAC policy in kilo-bits per second(kbps).
If the default value of '-1' is set, there is no constraint on
bandwidth allocated.
If the value of tmnxSubMcacPlcyUnconstrainedBW is set to '0' and if
an MCAC policy is assigned on the subscriber, then
no group (channel) from that policy is allowed on that subscriber.