[autotest] Setup chromeos_lab_servers database

This CL adds necessary script to create a chromeos_lab_servers database when
setting up Autotest.

This CL also changes the database_connection module so that any database
connection created by a given configure section will be force to use the
database credential defined in AUTOTEST_WEB (the AFE database).

design doc:
https://docs.google.com/a/google.com/document/d/1fqeXZElMkx5lVEh8xSdNMDn88LE6xJLkU-5vc3iVmOw/edit#

BUG=chromium:424700
TEST=locally run:
./site_utils/setup_dev_autotest.sh -p autotest -a /usr/local/autotest/
./database/migrate.py sync 0 -d AUTOTEST_SERVER_DB
./database/migrate.py sync 1 -d AUTOTEST_SERVER_DB

Confirm the database and tables are created for version 1 and deleted for version 0.

DEPLOY=migrate_server_db

Change-Id: Iea923b2bd5eca81689ac888322f7ae66e6938f10
Reviewed-on: https://chromium-review.googlesource.com/225971
Tested-by: Dan Shi <dshi@chromium.org>
Reviewed-by: Prashanth B <beeps@chromium.org>
Commit-Queue: Dan Shi <dshi@chromium.org>
6 files changed