Make bdrv_get_full_backing_filename_from_filename() return an allocated
string instead of placing the result in a caller-provided buffer.
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Message-id: 20190201192935.18394-11-mreitz@redhat.com
Signed-off-by: NMax Reitz <mreitz@redhat.com>