Increase riak test timeout to 600
Increase riak test timeout to 600

We need to fetch data from external source, so sometimes we may need
more time

Change-Id: I94b2e90fd33bd83a23662a1875fdab935bf4b2ad

pigmej/solar,pigmej/solar,openstack/solar,openstack/solar,pigmej/solar,openstack/solar