This is the time interval at which this entity sends out
IGMP host query packets. For a router, snDvmrpEnable must
have been set to 'enabled' before this object is writen.
For a switch, snSwGroupIpMcastMode must have been set to
'enabled' and snSwIpMcastQuerierMode must have been set
to 'querier' before this object is writen.