* Update to avoid pseudo-random number
This PR update the usage of rand so that non-global seed is used.
Signed-off-by: Yong Tang <yong.tang.github@outlook.com>
* Add concurrency-safe random source
See https://stackoverflow.com/questions/48958886/how-to-create-a-thread-safe-rand-source
Signed-off-by: Yong Tang <yong.tang.github@outlook.com>
