migrate from random crate to rand

[RealAdarsh]

Migrate from random crate to rand #378

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[adamcrume]

Can you fix the test failures? The ./test-all script should succeed.

[RealAdarsh]

Hello Adam, I am new to open-source, Could you please help me how to fix this? I could try fixing it.

[adamcrume]

All the other places in the file that reference the random crate also need to be switched to the rand crate, and Cargo.toml needs to be updated. This isn't a simple find-and-replace, because the types and functions in the two crates aren't identical.

[adamcrume]

This was fixed in https://github.com/tensorflow/rust/pull/384.