async_wrap: fix Promises with later enabled hooks

Assign a `PromiseWrap` instance to Promises that do not have one
yet when the PromiseHook is being called.

Fixes: https://github.com/nodejs/node/issues/13237
PR-URL: https://github.com/nodejs/node/pull/13242


Reviewed-By: Andreas Madsen <amwebdk@gmail.com>
Reviewed-By: Matthew Loring <mattloring@google.com>