CA-76600: preserve the rtc/timeoffset over migrate
CA-76600: preserve the rtc/timeoffset over migrate

Unfortunately the rtc/timeoffset can be changed dynamically by
the guest (via qemu) but isn't stored in the domain save record.
Therefore we need to both update our domain persistent state
in xenopsd (for migrate/resume) *and* update our VM config in
the higher-level toolstack (ie xapi) for start.

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

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