cc: @ralf-meyer

Minor fixes of eABF module

There was some "return 1". Now that exit code is checked, this would
have triggered an error

Report a failure in the following two cases:
- unknown test type
- test program exiting with non-zero code

Fix for issue #306 with VES

Minor changes to VES module

Api version incremented for consistency, even though there was
no change in between v2.3 and v2.4

Fix #296.

Fix #296.