Fix for https://issues.infn.it/jira/browse/STOR-514

The srmLs SURLs' details are returned if presents
Added volatile and synchronized keywords and other optimizations.

- Removed the exception raised when surls' details are not provided
after a srmLs exited with SRM_SUCCESS or SRM_PARTIAL_SUCCESS
Merge pull request #3 from italiangrid/fix/STOR-514

Fix for https://issues.infn.it/jira/browse/STOR-514