vfi hotplug: drop support for XS 5.5.0 from vswitch functionlity.
vfi hotplug: drop support for XS 5.5.0 from vswitch functionlity.

This was imported from the vswitch tree (which wants to work on XS
5.5.0) for ease of import but back them out here.

koushikcgit/xcp-rrdd,koushikcgit/xcp-rrdd,sharady/xcp-networkd,djs55/squeezed,johnelse/xcp-rrdd,djs55/xcp-networkd,sharady/xcp-networkd,koushikcgit/xcp-networkd,djs55/xcp-networkd,simonjbeaumont/xcp-rrdd,djs55/xcp-rrdd,johnelse/xcp-rrdd,robhoes/squeezed,simonjbeaumont/xcp-rrdd,djs55/xcp-rrdd,koushikcgit/xcp-rrdd,koushikcgit/xcp-networkd