IPMI Plugin - Auto Discovery of BMC nodes

With this checkin the IPMI Plugin in aggregator node will automatically
figure out the Compute Nodes' BMC's IP Address under it.

Adding more detail..
Each IPMI plugin in the compute node will read the BMC's IP address
through the KCS driver and send it along with the data blob collected
by the heartbeat plugin. After this the IPMI plugin disables itself(in
compute node only).

The Aggregator's IPMI plugin will collect and unpack this packed
credentials and update a list of BMC nodes it needs to monitor, which
correspond to the compute nodes under its jursidiction.
IPMI Plugin

Fixed a potential segmentation fault issue.
Modified the order of storing data, where the sampling time gets
stored prior to nodename, to comply with existing methods
IPMI Plugin

Fixed some klockwork issues, and also moved a global variable
declaration to the header file to facilitate unit testing.
IPMI Plugin

Addressing some code review comments
Merge branch 'vin_ipmi_auto_2'