, please be aware that VMware Communities is not a means of contacting VMware support - you should open a Support Request for that - also as this is a VxRail cluster your support contract is a very likely with Dell EMC and not VMware directly and thus Dell EMC should be contacted.
Anyway. If you can't disable RDMA via the client (e.g. because you have vCenter issues because this is running on the cluster and you have issues impacting the cluster) you could try disabling it on all the nodes individually by running:
# vsish -e set /vmkModules/rdt/enableRdma 0