Now that all the release-specific upgrade rules are in the 'db_hiupgrade' (from where they can use the type-safe Db.* API), remove the unneeded low-level logic.
Now that all the release-specific upgrade rules are in the 'db_hiupgrade' (from where they can use the type-safe Db.* API), remove the unneeded low-level logic.

Signed-off-by: David Scott <63c9eb0ea83039690fefa11afe17873ba8278a56@eu.citrix.com>

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