refactor: Make CAddrMan::cs non-recursive

Author: hebasto

src/addrman.h

@@ -626,8 +626,8 @@ class CAddrMan
     FastRandomContext insecure_rand;
 
 private:
-    //! critical section to protect the inner data structures
-    mutable RecursiveMutex cs;
+    //! A mutex to protect the inner data structures.
+    mutable Mutex cs;
 
     //! Serialization versions.
     enum Format : uint8_t {