local_app: always specify --host to dev_appserver.py.
local_app: always specify --host to dev_appserver.py.

When environment DEVSHELL_CLIENT_PORT is set,
google/appengine/tools/devappserver2/cli_parser.py to change the default value
to 0.0.0.0 for the 3 sockets it binds to via --host, --admin_host and
--api_host, which is surprising.

R=9f116ddb1b24f6fc1916a676eb17161b6c07dfc1@chromium.org
Bug:
Change-Id: I67773c8165333aff03f91c2dbca467a58beca963
Reviewed-on: https://chromium-review.googlesource.com/759087
Reviewed-by: Vadim Shtayura <9f116ddb1b24f6fc1916a676eb17161b6c07dfc1@chromium.org>
Commit-Queue: Marc-Antoine Ruel <d2bf0fc09b08f7b0888b3ddab32b3e89c7122c8b@chromium.org>

luci/luci-py,luci/luci-py,luci/luci-py,luci/luci-py