Put all databases under "databases", not "database"
Put "device" part after the base path of databases.

And, migrate database location from multiple cases.
Put "device" part after the databases base path, and migrate database locations correctly
Simplify
Migrate database location for Catalog V1 also
Fix syntax error
Suppress warning

$ bundle exec rake test:unit
/usr/bin/ruby2.0 /home/piro/groonga/droonga-engine/test/unit/run-test.rb
/home/piro/groonga/droonga-engine/lib/droonga/catalog/base.rb:49: warning: shadowing outer local variable - old_db_path
Detect path to databases correctly
Simplify