Description of problem:
This is branching from bug 616273 comment 98.  Please see this bug for the original context.

anaconda crashes when formatting a partition on multipath device.  anaconda aborts with "Formatting Failed".  It says "An error was encountered while formatting device /dev/mapper/mpathop1." and "invalid device specification"

The problem was last confirmed with RHEL6 Snapshot10 with the bz616273.img
mentioned in this comment:
https://bugzilla.redhat.com/show_bug.cgi?id=616273#c93

The same phenomenon has occurred with different operations / conditions.
See the following comment for details:
https://bugzilla.redhat.com/show_bug.cgi?id=616273#c96


Version-Release number of selected component (if applicable):
anaconda 13.21.68
RHEL 6 Snapshot 10 + bz616273.img

How reproducible:
every time (?)

Steps to Reproduce:
1. Prepare 2 multipath devices
2. Clear partitions on both devices ('mklabel msdos' from parted)
3. Start RHEL6 installation
4. Select "Specialized Storage Device"
5. Select both multipath devices in device selection
6. Select "Create Custom Layout"
7. Create "/" on mpath#1, which appears lower of the 2 devices
   in the device listing
8. Create "/boot" on mpath#0, which appears higher of the 2 devices
   in the device listing
9. Click "Next"

Actual results:
anaconda crashes and gives 'invalid device specification' error

Expected results:
installation proceeds normally

Additional info:
19:09:45,044 CRITICAL: anaconda 13.21.68 exception report
Traceback (most recent call first):
  File "/tmp/updates/storage/formats/__init__.py", line 266, in create
    raise FormatCreateError("invalid device specification", self.device)
  File "/tmp/updates/storage/formats/fs.py", line 838, in create
    DeviceFormat.create(self, *args, **kwargs)
  File "/tmp/updates/storage/deviceaction.py", line 290, in execute
    options=self.device.formatArgs)
  File "/tmp/updates/storage/devicetree.py", line 700, in processActions
    action.execute(intf=self.intf)
  File "/tmp/updates/storage/__init__.py", line 298, in doIt
    self.devicetree.processActions()
  File "/tmp/updates/packages.py", line 109, in turnOnFilesystems
    anaconda.id.storage.doIt()
  File "/tmp/updates/dispatch.py", line 208, in moveStep
    rc = stepFunc(self.anaconda)
  File "/tmp/updates/dispatch.py", line 126, in gotoNext
    self.moveStep()
  File "/tmp/updates/gui.py", line 1338, in nextClicked
    self.anaconda.dispatch.gotoNext()
FormatCreateError: ('invalid device specification', '/dev/mapper/mpathop1')