Update test_role_plugin test to include a comma in a privilege
    
    Introduce a comma into a privilege name to assure we can handle
    commas.
    
    Commas must be escaped for some parameters, add escape_comma() utility
    and invoke it for the necessary parameters.
    
    Utilize a DN object to properly construct a DN and most importantly to
    allow equality testing beween the DN we expect and the one
    returned. This is necessary because a DN can be encoded according to
    different encoding syntaxes all of which are valid. DN objects always
    decode from their input. DN objects can test for equality between DN's
    without being affected by DN encoding.
    
    Add a equality callback for the dn in the expected dict. When the test
    framework tests for equality between the expected value and the
    returned value it will call back into a function we provide which will
    convert the returned dn into a DN object. An equality test is then
    performed between two DN objects. This is the only way to properly
    compare two dn's.