XTR fails to run when MYSQL has a complex password

[dasgarner]

OP: https://community.xibo.org.uk/t/xtr-breaks-with-complex-mysql-passwords/31366

[dasgarner]

We can probably solve this for maintenance in entrypoint.sh around lines 244/245:

        /usr/bin/declare -px | grep -E "^declare -x MYSQL" >> /var/www/maintenance.sh
        /usr/bin/declare -px | grep -E "^declare -x MEMCACHED" >> /var/www/maintenance.sh

However, we would then need to support complex passwords throughout the whole stack.

We also document that passwords should be alpha numeric, so I am modifying this to not a bug and delaying it for a more detailed investigation.

Decided after a discussion with #ops.