Fix various copy instead of const ref reported by cppcheck (part 3) (#5616)

* Also remove 2 non declared but defined functions
* Make some functions around const ref changes const

src/util/thread.h

@@ -29,9 +29,10 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #include "container.h"
 
 template<typename T>
-class MutexedVariable {
+class MutexedVariable
+{
 public:
-	MutexedVariable(T value):
+	MutexedVariable(const T &value):
 		m_value(value)
 	{}
 
@@ -41,21 +42,14 @@ public:
 		return m_value;
 	}
 
-	void set(T value)
+	void set(const T &value)
 	{
 		MutexAutoLock lock(m_mutex);
 		m_value = value;
 	}
 
-	// You'll want to grab this in a SharedPtr
-	MutexAutoLock *getLock()
-	{
-		return new MutexAutoLock(m_mutex);
-	}
-
 	// You pretty surely want to grab the lock when accessing this
 	T m_value;
-
 private:
 	Mutex m_mutex;
 };