refactor: Replace RecursiveMutex with Mutex in Shutdown()
refactor: Replace RecursiveMutex with Mutex in Shutdown()

Former-commit-id: 7366c7ba4a1b196253580b603a017dd70b8b87d4
syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin