ClearCase: Fixed get active VOBs

The correct way to check if a VOB is active (mounted) is to check for
a "*" in the output of "cleartool lsvob". On windows a directory for
each active VOB exists under topLevel, but this is not true for unix
where directories (mount points) for all VOBs exists always.

Change-Id: Iccb0e38a39dfcae72326d68b9ff43b2555187f6c
Reviewed-by: Orgad Shaneh <orgads@gmail.com>