Remove root password validation

I know start a mysql container with no-password root user is very dangerous. But in some case, such as in development or test environment, i do need to make that kind of mysql container. So i think we should remove the check on root password. A warning massage when starting container or in document is enough
Should be: `if [ -z "$MYSQL_ROOT_PASSWORD" -a -z "$MYSQL_ALLOW_EMPTY_PASSWORD" ]; then`  (a little simpler)

Also, could you remove the extraneous whitespace changes?

Thanks for the contribution.