dreport: add fanctl dump output to BMC dump

Execute "fanctl dump" command and append the output json
file to the BMC dump.

Tested:
Fan control dump written to: /tmp/fan_control_dump.json
{
    "flight_recorder": [
        "Mar 24 14:12:55.323331:        main: Startup",
.
.
.

}

Signed-off-by: Marri Devender Rao <devenrao@in.ibm.com>
Change-Id: I52e972382f9e9c2aabab8c9034fd4da7775203e5