Bug 870476

Description of problem:

If anaconda finds a disk that has a whole-device file system, it will be unable
to handle the situation. For example, i created an ETX4 file system on /dev/vdb.
Please remember that while in this case i created such file system for testing
purposes, there is no guarantee that anaconda will not find one of these in 
the  future (for reasons unknown, error, mistake, ignorance, others, for part of the user, these things will exists).

Anaconda will be unable to perform AUTOMATIC PARTITIONING on the device, also 
performing MANUAL PARTITIONING will also not work.

When selecting vdb (in this case), STORAGE: INSTALLATION DESTINATION will claim
that there is not enough free space to install fedora. The space must be reclaimed.

But vdb is seen by AUTOMATIC PARTITIONING as having one "0 B Total" 'reclaimable
space' and there is NO ACTION possible. For anaconda, the disk is 100% UNUSABLE.
It cannot even WIPE the disk, which is UNPARTITIONED! Anaconda cannot create
a disk label over a file system (which in this case is necessary).

Selecting  MANUAL PARTITIONING for vdb shows the disk as having no partitions (which is correct), but the "click here to create them automatically" fails with "no disks selected" (which is NOT TRUE).

Manually creating a /boot (512mb) swap (512mb) and /5gb is not possible, anaconda fails with "KeyError: '/dev/vdb'", i did not use ABRT nor reported this specific case.

Also anaconda does not print any error that might help the user to solve the issue. Even an "Please do X, Y, Z and launch anaconda again. Bye!". 

Version-Release number of selected component (if applicable):
F18b TC6

How reproducible:
always

Steps to Reproduce:
0. create an EXT4 file system on (for example) /dev/vdb. (/dev/vda has free space).
1. Enter STORAGE: INSTALLATION DESTINATION and select /dev/vdb
2. Do as above. (I tried with default boot parameters and with gpt boot parameter, just in case).
  
Actual results:
vdb disks ins UNUSABLE by anaconda.
The UI behavior does not help the user to diagnose why it is happening.

Expected results:
Either anaconda let the user wipe the disks or at least an specific error, 
so the user can perform some actions manually.

Additional info:

I tried selecting both disks and anaconda installed 'ok' on the first one and did not touch the second one (vdb). But i am not 100% sure what will happen in all cases (for example a whole-device usb drive and/or combined with multiple disks).