[Docker] Update init scripts

[Roxedus]

Consider migrating from the legacy scheme from the old cont-init.d(S6V2) to the new s6-overlay/s6-rc.d(S6V3) scheme to ensure order of operations.

The legacy scheme runs parallel to the new scheme, meaning that 30-config gets executed at the same time as user-manipulation happens in the base image, giving you inconsistent file ownership. (The parallelism can be observed when increasing the verbosity of s6 -e S6_VERBOSITY=3)

Here is an example on a migration

You can also overwrite the branding like this