[FIX] cli/server: handle comma-separated `db_name` config properly
[FIX] cli/server: handle comma-separated `db_name` config properly

The db_name parameter passed in command-line (-d) or in configuration file,
supports a list of database names separated by commas, in order to
preload them. The WorkerCron processes will also respect this list and only
connect to the specified database(s).

As of Odoo 9 the server also automatically initializes a new database
if the one passed via `db_name` does not exist or is not initialized.
This code did not properly handle multiple comma-separated value,
and created an unitialized database named `a,b` when db_name was set
to `a,b`.

Fixes #13079
Closes #13094

dfang/odoo,hip-odoo/odoo,microcom/odoo,storm-computers/odoo,microcom/odoo,hip-odoo/odoo,bplancher/odoo,storm-computers/odoo,laslabs/odoo,laslabs/odoo,microcom/odoo,laslabs/odoo,storm-computers/odoo,Elico-Corp/odoo_OCB,Elico-Corp/odoo_OCB,bplancher/odoo,storm-computers/odoo,microcom/odoo,microcom/odoo,microcom/odoo,laslabs/odoo,dfang/odoo,laslabs/odoo,dfang/odoo,dfang/odoo,storm-computers/odoo,ygol/odoo,ygol/odoo,ygol/odoo,hip-odoo/odoo,storm-computers/odoo,laslabs/odoo,bplancher/odoo,hip-odoo/odoo,Elico-Corp/odoo_OCB,bplancher/odoo,Elico-Corp/odoo_OCB,ygol/odoo,hip-odoo/odoo,ygol/odoo,dfang/odoo,bplancher/odoo,Elico-Corp/odoo_OCB,dfang/odoo,ygol/odoo,hip-odoo/odoo,bplancher/odoo,ygol/odoo,Elico-Corp/odoo_OCB