sync operation with scope will fail with 'cannot find module' when migrate down

using version 0.10.0-beta.20

## command
```
db-migrate sync:test 20170330114201 --env staging --migrations-dir /Users/jianshen/projects/apollo/shared_schema/migrations --verbose --dry-run --config /Users/jianshen/temporary/database.json
```

## error
```
[ERROR] Error: Cannot find module '/Users/jianshen/projects/apollo/shared_schema/migrations/test/test/20170330132412-add-testtable-column-foo'
at Function.Module._resolveFilename (module.js:338:15)
at Function.Module._load (module.js:280:25)
at Module.require (module.js:364:17)
at require (module.js:380:17)
at Class.extend.setup (/Users/jianshen/projects/apollo/apollo-manager/node_modules/db-migrate/lib/skeleton.js:157:12)
at /Users/jianshen/projects/apollo/apollo-manager/node_modules/db-migrate/lib/migrator.js:220:33
at tryCatcher (/Users/jianshen/projects/apollo/apollo-manager/node_modules/bluebird/js/release/util.js:16:23)
at Promise._settlePromiseFromHandler (/Users/jianshen/projects/apollo/apollo-manager/node_modules/bluebird/js/release/promise.js:510:31)
at Promise._settlePromise (/Users/jianshen/projects/apollo/apollo-manager/node_modules/bluebird/js/release/promise.js:567:18)
at Promise._settlePromise0 (/Users/jianshen/projects/apollo/apollo-manager/node_modules/bluebird/js/release/promise.js:612:10)
at Promise._settlePromises (/Users/jianshen/projects/apollo/apollo-manager/node_modules/bluebird/js/release/promise.js:691:18)
at Async._drainQueue (/Users/jianshen/projects/apollo/apollo-manager/node_modules/bluebird/js/release/async.js:133:16)
at Async._drainQueues (/Users/jianshen/projects/apollo/apollo-manager/node_modules/bluebird/js/release/async.js:143:10)
at Async.drainQueues (/Users/jianshen/projects/apollo/apollo-manager/node_modules/bluebird/js/release/async.js:17:14)
at process._tickCallback (node.js:419:13)
```

---
Want to back this issue? **[Post a bounty on it!](https://www.bountysource.com/issues/43634679-sync-operation-with-scope-will-fail-with-cannot-find-module-when-migrate-down?utm_campaign=plugin&utm_content=tracker%2F73887&utm_medium=issues&utm_source=github)** We accept bounties via [Bountysource](https://www.bountysource.com/?utm_campaign=plugin&utm_content=tracker%2F73887&utm_medium=issues&utm_source=github).