Change log - Stability improvements

Bug fixes

• Fixed possible deadlock on collection read https://github.com/qdrant/qdrant/pull/725, thanks @BurtonQin
• Stability patch for distributed deployment: https://github.com/qdrant/qdrant/pull/710, https://github.com/qdrant/qdrant/pull/737, https://github.com/qdrant/qdrant/pull/712
• Fixes in concurrent storage update & optimization: https://github.com/qdrant/qdrant/pull/736