Adding support for decommissioning

The pluggable hardware manager should be able be used for decommissioning,
such as erasing disks, updating firmwares, changing BIOS settings, and
anything else specific hardware needs. This works with the agent driver
to store state in Ironic and request out of band reboots (which may be
required to make BIOS/firmware updates work). Also allows the agent to do
some basic verification of the node's properties, to ensure they haven't
changed, such as a stick of memory dying.

Change-Id: Ia42a8e75d2b8887b2351de97c2137fe21a7f4041
(cherry picked from commit aa27598f2b56614d76214805b0d2a8dde99e1aae)
Add versioning to Agent decommission

As the agent will likely be rebooting while decommissioning (to apply BIOS/
firmware upgrades), it is possible the version of the agent will change
between boots. Including a version string in the Hardware Manager allows
the Hardware Manager builder to bump versions for any breaking changes.
I recommend that the entire decommission process be restarted if there
is a version mismatch, but that will be up to individual drivers to
implement.

This change also adds a new return value for Agent REST commands called
'DECOM_VERSION_MISMATCH' that will signal no command was run, and
Ironic should update its stored value. A 'hardware_manager_version'
will be returned with AsyncCommandResult, and should be set in the
Ironic driver_info field and sent with any decommission command.

Change-Id: I2ae0e93573e0348f023aa124a07bb16921b5c53e
(cherry picked from commit 05059e14d665ace405c4766cc2f089dfe8d2eb12)
Add command metrics to IPA API

This will allow the agent to report timing and counter data for commands
that are run on the agent (starting with Standby commands). It will allow a
properly configured agent to send metrics to a remote or locally packaged
statsd. It is also extensible, so other metrics systems can easily be used.

Change-Id: Ic08d4ff78b6fb614b474b956a32eac352a14262a
(cherry picked from commit dace446667134de04c9184231a0e82980fe0e17c)