In case of a qcow2 format we store the result uncompressed
Since the format conversion only takes the real bytes into
account such that the sparseness of the raw disk will not
result in the output format and can be taken one by one
This Fixes bsc#1128146
In addition the commit includes a refactoring for the
evaluation of the compress flag in the runtime config.
Instead of the global overwrite, the flag gets evaluated
individually at the time the result metadata is created
0296808e24