block/backup: Rely on commit/abort for cleanup

block/backup: Rely on commit/abort for cleanup

Switch over to the new .commit/.abort handlers for
cleaning up incremental bitmaps.

[split up from a patch originally by Stefan and Fam. --js]
Signed-off-by: Stefan Hajnoczi <[email protected]>
Signed-off-by: Fam Zheng <[email protected]>
Signed-off-by: John Snow <[email protected]>
Signed-off-by: John Snow <[email protected]>
Message-id: 1446765200[email protected]
Signed-off-by: Stefan Hajnoczi <[email protected]>
Signed-off-by: Kevin Wolf <[email protected]>