This ticket includes:
1. Investigate all conn->flags(~30), find those flags that may have race condition problem.
2. Create a new field atomic_flags for connection, move those flags that need to be atomic to this new field.
3. Add atomic operation MACROs for uint32_t since the connection flag is 32 bit and wiredtiger does not support atomic operation on a uint32_t yet.
4. Modify the current flag operations to ATOMIC_32 operations for those atomic_flags.
5. Run performance tests to evaluate the impact of this new approach. It is possible to see performance BFs for the changes made in this ticket. However we shouldn't trade correctness for performance and need to find a better solution if there's still a performance impact.