Add Infiniband ipoib support. Suppress ugly 'which' output.

Suppress: "which: no ovs-vsctl in (/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin:/opt/bin:/mnt/host/source/chromite/bin)"  when openvswitch is not installed.

Add support for Infiniband ipoib interfaces which doesn't work without this change.
The specific error returned was "RTNETLINK answers: Invalid argument"

ipoib interfaces default to ib1 in the guest unless -i option used.  Must not begin with "eth".
Should work with SR-IOV ipoib devices as well.

Actually, I'm thinking rather it might be better to perform the check further up after where it says IFNAME=$1 near the top of the file.  Change the else portion to contain something like:

case $IFNAME in 
    # Override if device name begins with ib.  Infiniband IPoIB devices must be prefixed ib as the IPoIB driver 
	# is fussy about the device name.
    ib*) CONTAINER_IFNAME=ib1 ;;

	# All other interfaces default to eth1
    *) CONTAINER_IFNAME=eth1 ;;
  esac
	
Do you think the script should always print out CONTAINER_IFNAME?
e.g. After the above case I could put a line like
 echo "Setting container interface name to $CONTAINER_IFNAME"

Also I think the mac address setting does not work either.  If you try it you'll get "operation not supported".  Should I attempt to check for that as well and prevent it from being used? As it still succeeds in moving the ib device to the namespace before the error is printed.

And I should probably update README.md with an infiniband example.  As one obvious difference compared to the ethernet type is that when you assign the IPoIB device to a container the whole device is moved into the container namespace and so it therefore disappears from the host until the container is stopped.  Which means that only one IPoIB interface can be assigned to one container.  The method to get around that limitation is to use SR-IOV and pass a Virtual Function device to each container.  I haven't yet tested that but I would think it should work.  I don't have hardware available to test it right now but I will be able to get that tested out soon.