Cluster Manager: - Almost all Cluster Manager related code moved to   the same section. - Many macroes converted to functions - Added various comments - Little code restyling
Cluster Manager:
- Almost all Cluster Manager related code moved to
  the same section.
- Many macroes converted to functions
- Added various comments
- Little code restyling

JackieXie168/redis,JackieXie168/redis,JackieXie168/redis,JackieXie168/redis