Add empty default attributes

This makes the tunables more obvious
Add support for RHEL to the platform_family call

The logic already worked on RHEL.  It just needed the case statements
updated
Add new information to the IPMI ohai plugin

Default GW, Subnet Mask, IP Address Source (static or dhcp).  Now
captures SEL information such as version, overflow engaged, percent SEL
full, and number of entries