Fixed all volume group run

Howdy,

Fixed the handling for "all" volume groups.
Added in handling for UNKNOWN status and exiting with a fair error message in that case.


Later.
Great thanks for another commit.

Would you mind not changing this line? I've intended this fction to check only for first argument. 
If you would input multiple args, you wouldn't get positive result for neither. 

I will gladly merge rest to my repo.