Description of Problem:

When installing on a new disk, the partition table isn't re-read properly,
making the installer abort at the time of creating filesystems.

An instance of the  python disk object seems to be kept live too long and
as a side effect, parted refuses re-read the partition table (parted
sees the device fd still open.)

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

current.

How Reproducible:

Easily

Steps to Reproduce:
1. Start installing on a brand new disk or a disk whose partition table has
   been ereased (dd if=/dev/zero of=/dev/<device> bs=512 count=<enough>)
2. Go through the installation steps
3. The installer will abort trying to format the first partition of the new
   disk.

Actual Results:

Red Hat Linux isn't installed.

Expected Results:

Parition table should be re-read correctly, allowing the creation of 
filesystems on the partitions.

Additional Information:

This has been effectively traced with gdb to a device fd still marked used by
parted, because an instance of a Python object sharing it is still alive.

We don't know yet how this instance is still kept alive.