v21.2.0084-rc+302943

• Improved error handling in dfs
• Improved logging
• Improved health tracking and inconsistency prevention
• Improved index lifetime and stability across the clusters
• Increased maintain interval from 16 hours to 24 hours
• Added new integrity option to admin-cli structure+integrity
• Added tree list support to head-node and filesystem tool
• Added hook support with the extension capable for the 3rd party developers to watch dfs folder changes
• Added HOOKS_PATH env variables to head-node
• Added RabbitMQ hook provider to head-node hooks
• Fixed deadlock between data-nodes and manager-node
• Changed and separated go module usage in the project
• Cleaned up and refactored the code for the performance improvement

THIS VERSION IS A STABLE PRODUCTION-READY RELEASE CANDIDATE VERSION