This patch removes `proxysql_project_database_internal_tls_enable`
variable and also 'use_ssl: 1' option from ProxySQL's user
configuration. The reason for this removal is that when
'use_ssl: 1' option is enabled on the ProxySQL frontend
side, ProxySQL does not allow non-TLS connections.
This, of course, breaks upgrades or reconfigurations
when an operator enables TLS, as it blocks all non-TLS service
connections at the moment of switching.
Simply said, we do not need to, nor can we, strictly enforce
user connections over TLS because it disrupts reconfiguration
and upgrades. Instead, it is sufficient to reconfigure
the service to connect over TLS - which is already implemented.
It also corrects the `database_enable_tls_internal`
variable, ensuring it is enabled only when
`kolla_enable_tls_internal` is enabled, rather than
`kolla_enable_tls_backend`.
Closes-Bug: #2086466
Change-Id: I6c56b144a81f800e062d6670733ca606733c9e1b
624056be02