multiple channel configuration support

Previously, the ipmi daemon only supported eth0 and hard-coded it
to channel 1.  This allows one to map via a configuration.  The
channel number provided is checked against a configuration to retrieve
the ethernet device identifier, e.g. eth0.

Tested: Ran on a quanta-q71l and was able to properly set MAC, IP,
Netmask, Gateway IP, and then verified the data was set for the eth1
via `ip addr show eth1`.

Change-Id: I92f63188297304e9454fd0d6fe32bc6cf84bb181
Signed-off-by: Patrick Venture <venture@google.com>
7 files changed