Explicitly select "HT40-" for 5GHz HT40 tests

hostapd has extra checks that prevent use of the wildcard
"[HT40+][HT40-]" for ht_caps in some situations.  Explicitly
select [HT40-] for channel 48 since it should be paired with
channel 44.

BUG=chromium-os:13910
TEST=Rerun test

Change-Id: I6141ebc77f15e065f6dc9e486c618a19fd4f70b9

R=sleffler@chromium.org

Review URL: http://codereview.chromium.org/6805022
10 files changed