add gating up/down script for devstack

This adds the test infrastructure for testing that unstack.sh and
clean.sh do the right thing, and actually stop what's expected. This
is designed to be used in upstream testing to make unstack and clean a
bit more certain.

It includes numerous fixes to make these pass in an errexit
environment with the gate config. The scripts still don't run under
errexit because we don't assume we've handled all possible cleanup safely.

Change-Id: I774dfb2cc934367eef2bb7ea5123197f6da7565b

lib/databases/mysql

@@ -28,17 +28,14 @@ function cleanup_database_mysql {
     stop_service $MYSQL
     if is_ubuntu; then
         # Get ruthless with mysql
-        stop_service $MYSQL
         apt_get purge -y mysql* mariadb*
         sudo rm -rf /var/lib/mysql
         sudo rm -rf /etc/mysql
         return
     elif is_fedora; then
-        stop_service mariadb
         uninstall_package mariadb-server
         sudo rm -rf /var/lib/mysql
     elif is_suse; then
-        stop_service mysql
         uninstall_package mysql-community-server
         sudo rm -rf /var/lib/mysql
     else