Make datasource creation failure a non-fatal error
Make datasource creation failure a non-fatal error

Previously, if a datasource failed to startup, Congress would
fail to startup too.

This change allows Congress to startup, even if one or more of
the datasources does not.

Closes-Bug: 1671344

Change-Id: I95aeb6a0c180ed177f59e129b4330748e459275e

openstack/congress,openstack/congress