nvmf: Sync before unloading the NVMf initiator

This is a bit heavy handed, but really make sure all
activity has ceased.

Change-Id: Iaa1ce16fd9e059f9eaec6712226344d69075b243
Signed-off-by: Ben Walker <benjamin.walker@intel.com>

test/nvmf/common.sh

@@ -81,6 +81,9 @@ function allocate_nic_ips()
 
 function nvmfcleanup()
 {
+	sync
+	sleep 5
+	sync
 	rmmod nvme-rdma
 }