xenserver: Remove "Required-" parameters from "openvswitch" init script.

xenserver: Remove "Required-" parameters from "openvswitch" init script.

Commit 72dfb3b (xenserver: Add LSB init info to scripts.) added LSB init
info to the XenServer scripts.  This was verified to work on XenServer
5.5, but newer versions of XenServer interpret these values and alter
when "openvswitch" gets called.  This causes XenServer to not come up
with its networking configuration properly.

By removing the "Required-" parameters, OVS will properly come up.  This
is just a temporary fix, and a more proper one will be forthcoming.