Merge pull request #1320 from openshift-cherrypick-robot/cherry-pick-1308-to-18.0-fr5

[18.0-fr5] Enable IGMP snooping for uni01alpha pre-adoption deployment

Author: openshift-merge-bot[bot]

scenarios/uni01alpha/config_download.yaml

@@ -62,6 +62,7 @@ parameter_defaults:
   ComputeCount: 2
   NetworkerCount: 3
   NeutronGlobalPhysnetMtu: 1500
+  NeutronEnableIgmpSnooping: true
   CinderLVMLoopDeviceSize: 20480
   CloudName: overcloud.example.com
   CloudNameInternal: overcloud.internalapi.example.com