xenserver: Split kernel/userspace into separate RPMs for supplemental packs.

xenserver: Split kernel/userspace into separate RPMs for supplemental packs.

XenServer has the concept of a "supplemental pack", which is just a collection
of RPMs rolled into an ISO image for installation as a unit, either during
XenServer installation or later as an update.

The script used to build supplemental packs requires that a single RPM not mix
kernel and userspace components. It also enforces a particular naming scheme
for kernel module RPMs. This commit modifies the OVS RPM spec file to create
separate RPMs in accordance with these conventions.

In an attempt to ensure that the userspace and kernel module packages are both
present and compatible, the kernel package provides a fictitious capability,
openvswitch_mod.ko.0, and the userspace package requires that capability. If a
future change breaks backward compatibility between userspace and kernel, we'll
increment the numeric suffix, preventing mismatched installs.

Reviewed by Ben Pfaff.