Description of problem:
Whenever you want to gain root privileges using polkit, you are forced to enter the password using the terminal, thus breaking a lot of graphical applications which were gaining root at runtime, instead of being executed directly by root (packagekit, for example, the whole system-* Fedora's specific applications to manage firewall, users, ..)

Version-Release number of selected component (if applicable):
0.100

How reproducible:
Update Polkit from 0.98 (latest version available in Fedora 14) to 0.100 (latest version available in rawhide, this version is required by GNOME3)

Steps to Reproduce:
1. run in a terminal 'pkexec echo test', in a normal execution a graphical window would pop up and ask user to enter root password;
2. notice that the password is asked directly into the terminal.
  
Actual results:
The `textual fallback authentication agent' is used, instead of polkit-gnome authentication agent.

Expected results:
A graphical popup asking the user to enter the root password.