Summary:
The atomic variable "is_prepared_" was keeping Configurable objects from being copy-constructed. Removed the atomic to allow copies.
Since the variable is only changed from false to true (and never back), there is no reason it had to be atomic.
Added tests that simple Configurable and Customizable objects can be put on the stack and copied.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/8704
Reviewed By: anand1976
Differential Revision: D30530526
Pulled By: ltamasi
fbshipit-source-id: 4dd4439b3e5ad7fa396573d0b25d9fb709160576
3efc6fd641