Fix in system_tests.sh help and settings.
- Fixed behaivour of the environment variable 'NODE_VOLUME_SIZE'.
- Added short description of '-V' option in the script ./utils/jenkins/system_tests.sh

Change-Id: I3fc92734ee5f19a7a31d95724ae30967dbcf4f92
Merge "Fix in system_tests.sh help and settings. - Fixed behaivour of the environment variable 'NODE_VOLUME_SIZE'. - Added short description of '-V' option in the script ./utils/jenkins/system_tests.sh"