Description of problem:
Once we set a property (e.g. Roles Allowed, Run As) we cannot remove them.

Version-Release number of selected component (if applicable):
JBTIS 4.1.3.Beta3 (contains switchyard 1.1.0.v20130912-2244-H393-M2) 

How reproducible:
always

Steps to Reproduce:
1. In domain tab create new security configuration
2. Set Run As to 'user', press finish and save
3. Edit the configuration and remove tha field Run As
4. Press finish and save

Actual results:
The field Run As is still set to 'user'

Expected results:
The field Run As should be empty