CP-9906: Raise a ref rather than a UUID for VDI_NOT_IN_MAP

The CLI code has the ability to turn the ref into a UUID.

Signed-off-by: John Else <john.else@citrix.com>
(cherry picked from commit 30af00894c46132ae7cd62e6a3f5c8bb8259c1f7)
CP-9906: Improve SXM failure logging

Log that we don't know to where a VDI should be copied.

Signed-off-by: John Else <john.else@citrix.com>
(cherry picked from commit 6bd6d02860b4b49b54e240729d35af334d132c85)
CP-9906: Improve SXM failure error reporting

Raise a proper Api_error if we've failed to determine the destination to
which a snapshot VDI should be migrated.

Signed-off-by: John Else <john.else@citrix.com>
(cherry picked from commit 5042c2ca5fbe760e9c5ad7c935b894d62ac7c8e4)
Merge pull request #1980 from johnelse/sxm-workaround

Improvements to SXM failure logging and error reporting