more WiFi testing fixes

- fix client_check_* CL that was fubar
- openwrt fixups:
  + use "bridgedv" and "wiredev" a la bsd code and sample configs
  + set htcaps for ht20 and ht so 802.11n is enabled
  + split out config knobs that need support
  + purge dead client_check_config code
  + config['hw_mode'] may not be set, deal with it (not sure if this is
    the right fix but it allows tests like CheckPerf24HT20 to run)

Tested with WiFiMatFunc and WiFiSecMat suites; verified tests that
previously failed now pass.

Review URL: http://codereview.chromium.org/1763012
2 files changed