[megacli] new plugin for LSI MegaRAID based adapters

The MegaCLI utility is a proprietary utility provided by LSI which can perform reporting and management functions for MegaRAID SAS|SCSI adapters.
If the MegaCLI is detected, the plugin will collect basic information such as adapter status, firmware rev, battery status, and raid config.

Signed-off-by: Jon Magrini <jmagrini@redhat.com>