cta/CTA#130 Helgrind gets spurious when using `std::mutex` in the catalogue.

With respect to the rdbms::OcciStmt class. Replaced
std::mutex and std::lock_guard with their helgrind friendly
drop in replacements threading::Mutex and
threading::MutexLocker.

rdbms/OcciStmt.cpp

@@ -18,6 +18,7 @@
 
 #include "common/exception/Exception.hpp"
 #include "common/make_unique.hpp"
+#include "common/threading/MutexLocker.hpp"
 #include "rdbms/OcciColumn.hpp"
 #include "rdbms/OcciConn.hpp"
 #include "rdbms/OcciRset.hpp"
@@ -83,7 +84,7 @@ OcciStmt::~OcciStmt() throw() {
 //------------------------------------------------------------------------------
 void OcciStmt::close() {
   try {
-    std::lock_guard<std::mutex> lock(m_mutex);
+    threading::MutexLocker locker(m_mutex);
 
     if (nullptr != m_stmt) {
       m_conn.closeStmt(m_stmt);

rdbms/OcciStmt.hpp

@@ -18,10 +18,10 @@
 
 #pragma once
 
+#include "common/threading/Mutex.hpp"
 #include "rdbms/Stmt.hpp"
 
 #include <memory>
-#include <mutex>
 #include <occi.h>
 #include <stdint.h>
 
@@ -164,7 +164,7 @@ private:
   /**
    * Mutex used to serialize access to this object.
    */
-  std::mutex m_mutex;
+  threading::Mutex m_mutex;
 
   /**
    * The database connection.