Description of problem:
If a badly written CD is inserted, anaconda forces reboot instead of prompting
the user to replace the disk

Version-Release number of selected component (if applicable):
anaconda-11.0.5-1.ppc.rpm (or whatever is used on the PowerPC FC5)

How reproducible:
It happended the first and the only time I tried

Steps to Reproduce:
1. Start install from a good discs 1,2,3
2. Write truncated disk 4
3. Insert that disk when prompted
  
Actual results:
Reboot is the only option.  The text console shows that expat-devel couldn't be
installed.

Expected results:
User should be prompted to replace the disk.  It's easier to rewrite disk 4 that
to babysit the machine again through the install.

Additional info:
The bug is similar but distinct from bug #183974, which deals with network
installs.  Please don't forget to unlock the CD when prompting for replacement.