Read list type of environment variables

Read list type of environment variables

DBAAS Helm Charts appconfig has been changed to have individual ports
and master names for each SDL cluster due to problems seen with DBAAS
upgrade and rollback caused by re-allocation of the same address/port
of Redis to some other SDL cluster. Implement support for new list type
environment variables reading in SDL:
 * DBAAS_SERVICE_PORT
 * DBAAS_SERVICE_SENTINEL_PORT
 * DBAAS_MASTER_NAME

Issue-Id: RIC-698

Signed-off-by: Timo Tietavainen <timo.tietavainen@nokia.com>
Change-Id: I9a9d94e536e0e4e2a174ef0b6fb2beb4c73ef4f5