Add the missing seed argument for deterministic results.

[ice-tong]

Summary

Add the missing seed argument to self.image_data_generator.get_random_transform for deterministic results. Especially during multi-thread, we cannot set numpy.rand.seed out of the thread, this argument pass is important!

Related Issues

None

PR Overview

• [ ] This PR requires new unit tests [y/n] (make sure tests are included)
• [ ] This PR requires to update the documentation [y/n] (make sure the docs are up-to-date)
• [x] This PR is backwards compatible [y/n]
• [ ] This PR changes the current API [y/n] (all API changes need to be approved by fchollet)