This patch allows to skip the installation
of the database backend packages (MySQL or Postgres)
with the introduction of the INSTALL_DATABASE_SERVER_PACKAGES
variable (defaulted to True).
This is useful in such environments that do not require
to install the MySQL/Postgres server packages directly but using
a container serving that purpose, for those cases all the
remaining steps should be executed just skipping the
packages install.
Change-Id: I26628a31fdda3ce95ed04a2b7ae7b132c288581f
cc6e20b24d