Bug in dirac-dms-remove-replicas

dirac-dms-remove-replicas crashes with
```
Error: Failed to perform getPathPermissions from any catalog
Traceback (most recent call last):
  File "/home/sailer/software/DIRAC/DiracDevV6r8/DIRAC/DataManagementSystem/scripts/dirac-dms-remove-replicas.py", line 47, in <module>
    for lfn in sortList( res['Value']['Successful'].keys() ):
```
Or some other error message.

Do I understand correctly that if res['OK'] is False, then the previous function returned S_ERROR()
So there never is any res['Value'], so we have to continue after the error message
Right?
Otherwise there should be a check
```
if not 'Value in res:
  continue
```
in line 44 instead
Merge pull request #2166 from andresailer/patch-5

[v6r11] Bug in dirac-dms-remove-replicas