update_db.sh should read db connection string from rasmgr.conf

[Dimitar Misev]

Currently the update_db.sh db connect string is hard coded during installation, normally /opt/rasdaman/data/RASBASE.

The user can change the db connection in rasmgr.conf with option -connect to some other path though.

So for update_db.sh to work correctly, it needs to read rasmgr.conf; in the systemtest this is extracted with

export RASDB="$(grep define $RASMGR_CONF | grep connect | awk '{ print $5 }')"

If this fails, then as fallback update_db.sh can continue with the installation path as currently.