Fixed failing tests for GraftCommand by adapting the parsing of hg's output to the current format.
Was already merged in Bitbucket before import, marked as merged by the import user
The previous versions of hg probably used to output "grafting revision 1" as the first line in stdout. These days, we get «grafting 1:13876923c49e "Commit message #2"». The fix consisted mainly in adapting to the new format.