use exceptions instead of return True/False

the manage process_acls function was rather complicated by having
a mix of using exception handling and functions returning true/false
depending on the level of nesting. Making the inner functions all
return specific exceptions cleans up the top logic rather significantly.

Change-Id: I5ff6edbacbe874b7bb60e10bb282f35bd4b3ea11
Merge "use exceptions instead of return True/False"