Wipe any metadata from a nodes disk

Ensure that a nodes disk is wiped of any metadata. This Patch only
deals with the wiping of the metadata per review comments.

Closes-Bug: #1317647

Change-Id: I3bc2da3a12362bad12957d6f34e7ee7807813300
Set instance default_ephemeral_device

Duplicate the old nova-bm logic of setting the default ephemeral device
to /dev/sda1 (first partition on the disk) when an ephemeral partition
is being used. This is a short-term solution to fix the majority of cases
that depend on this value being present in the instance metadata
(e.g., cloud-init). Longer term, we should consider using something
like udev by-label names (/dev/disk/by-label/NNN) or similar.

Closes-Bug: #1324286

Change-Id: Ia85f0fd0bfa5cca0320db0e8c7f1e0e2b61b4ef6
Stop ipmitool.validate from touching the BMC

Stop the IPMITool driver from calling 'mc guid' in validate().

Validate is currently called synchronously when API requests are sent to
  GET /v1/node/NNN/validate

While work is ongoing to make the API more asynchronous, this presents
a particular issue in that a user can spam this URL and overwhelm the
hardware node's BMC.

Furthermore, validate() is called internally in several places, which is
further contributing to BMC instability as reported in the related
bug 1320513.

Change-Id: I2414d2b07e2ab86c85ca18bc033368ddf43f7f43
Closes-bug: #1314954
Related-bug: #1320513
remove default=None for config options

In the cfg module default=None is set as the default value, there are a 
lot of StrOpts but few with default=None, to be more unify and clear, we 
should remove it.

Change-Id: I2a5dab763fe9cc07e6c1dbed4628e9cf2ca28bcd
Closes-Bug: #1323975
Merge "Set instance default_ephemeral_device"
Merge "Stop ipmitool.validate from touching the BMC"
Merge "remove default=None for config options"
Merge "Wipe any metadata from a nodes disk"