cellular: Bump timeout in HTTP speed test.

Slower GPRS mode (1 downlink, 1 uplink) takes longer.

BUG=chromium-os:37745
TEST=cellular_Throughput (--technology=GPRS)

Change-Id: I072420650ce9f04982b73012dd418aa7bd36aab8
Reviewed-on: https://gerrit.chromium.org/gerrit/41059
Reviewed-by: Arman Uguray <armansito@chromium.org>
Commit-Queue: Thieu Le <thieule@chromium.org>
Tested-by: Thieu Le <thieule@chromium.org>
1 file changed