Recent changes to enable more than just MySQL to be used
in devstack moved some setup stuff to lib/database. While
this file was source'd in tools/configure_tempes.sh, the
BASE_SQL_CONN variable was not being set because
lib/database/initialize_database_backends was not called.
Change-Id: I53c3302097a94c842860fcb781e21383150bde7f
fixes: LP bug#1077056