1044574: Added --schema-only option to cpsetup/cpdb

On create, skip db creation step and only load the schema.
This is useful for situations where the database is created
by an external source, and only the schema should be applied.
Merge pull request #467 from candlepin/mstead/1044574-add-schema-only-option-to-setup-scripts

1044574: Added --schema-only option to cpsetup/cpdb