Green sky tests on the asan bot.

Skipped tests were not getting skipped because
the code gets whether the build is a debug or release
build from the configuration commandline argument, but
the asan bots pass Release_asan. Instead, read the
debug vs. release state from gn args instead of inferring
it from the out directory.

R=eseidel@chromium.org, esprehn@chromium.org, sky@chromium.org

Review URL: https://codereview.chromium.org/754673003