Add SMAPI call SR.update_snapshot_info

Signed-off-by: John Else <john.else@citrix.com>
Move a comment to the line it refers to

Signed-off-by: John Else <john.else@citrix.com>
Add remote SR/VDI to mirror_record type

Signed-off-by: John Else <john.else@citrix.com>
CA-78901: Fix snapshot info for SXM'ed snapshot disks

Once we have copied all snapshot disks to the remote SR and mirrors are
running for all live VDIs, rebuild the snapshot tree on the remote SR
for each live VDI.

Signed-off-by: John Else <john.else@citrix.com>
Ignore Unknown_RPC exceptions in update_snapshot_info

Signed-off-by: John Else <john.else@citrix.com>
Rename update_snapshot_info -> update_snapshot_info_src

Signed-off-by: John Else <john.else@citrix.com>
Fix partial application

Signed-off-by: John Else <john.else@citrix.com>
Better logging for update_snapshot_info_src

Signed-off-by: John Else <john.else@citrix.com>
Add SMAPI call update_snapshot_info_dest

Signed-off-by: John Else <john.else@citrix.com>
Rearrange snapshot updating SMAPI code

- Implement SR.update_snapshot_info_dest
- Call the above from SR.update_snapshot_info_src
- Remove VDI.set_snapshot_of, VDI.set_snapshot_time,
  VDI.set_is_a_snapshot from SMAPI

Signed-off-by: John Else <john.else@citrix.com>