[v1.0.4] disable queue dispatcher for 1 worker thread

Improvements:

• Turn Stream close from protected bool to atomic bool (more efficient)
• Disable queue dispatcher when only 1 worker thread is configured (more efficient and also minimize crash bug due to client connection break on high load)
• Simplify Stream constructor regarding io service reference which could be accessed through response structure.

Changelog: v1.0.3...v1.0.4