Restore mock network operations removed by commit d4d8e38897152671a2f99edeab95c3a146a231cf

part of DTACLOUD-470 https://issues.apache.org/jira/browse/DTACLOUD-470
Make configured frontends available as method on Deltacloud
* lib/cimi/helpers/database_helper.rb (test_environment?): remove, unused
Encapsulate the test for whether we need a DB in Deltacloud::need_database?
* tests/test_helper.rb: run all initializers under the test environment

This makes it possible to run individual tests again