Get ready for last round of tests in 9th floor.

* Extract RSSI from beacon and non-beacon frames
* Fix handling of 802.11ac channels reported by `airport`
* Suppress lint errors from outside files
* Continue report if iperf3 files contain invalid JSON.

Change-Id: Ie50585252a5a2e83f736c76b94c972a7ce3cc73d
6 files changed