SNMPv3 message authentication and encryption features
added to Ironic ``snmp`` driver.
Added support for the ``context_engine_id`` and
``context_name`` parameters of the SNMPv3 message
at Ironic's ``snmp`` driver.
The ``snmp_security`` parameter of Ironic ``snmp``
driver is obsoleted by the ``snmp_user`` parameter.
Though ``snmp_security`` parameter remains supported.
For the sake of patch reviewability, it does not touch
similar SNMP features in the `iLO` and `irmc` drivers.
A followup patch might converge these similar SNMP uses
onto the core ``snmp`` driver's functionality this patch
introduces.
Change-Id: Ic8a4fc37a42377c4ec50ffae421b3f47922ef982
Story: 1710850
Task: 10611
635f4a9e17