Description of problem:
In Configure -> smart class parameter, deleting the existing matcher and without saving the changes, creating the same again throws error 'Match has already been taken'.

Version-Release number of selected component (if applicable):
foreman-1.11.0-0.develop.201510221551git1d0315e.el7.noarch

How reproducible:
Always

Steps to Reproduce:
1. Create matcher for puppet class parameter with some attribute and some value.
2. Save the changes.
3. Again edit the puppet class parameter to delete the matcher created in step 1.
4. Without saving changes of step 3 in parameter, create the matcher with same attribute and same value as created in step 1 and try to save the change to the parameter.

Actual results:
The error of 'Match has already been taken' is displayed and not allowing to save the changes.

Expected results:
Deleting and creating of matcher with same attribute and value should be allowed without saving the changes to parameter.