Make logging shutdown more cleanly

After shutting down the logging thread, delete each logging output entity in
turn.  This will cause the db logging thread to be cleanly shutdown as well.

mythtv/libs/libmythbase/mythlogging.cpp

@@ -336,11 +336,12 @@ void DBLoggerThread::run(void)
 bool DatabaseLogger::isDatabaseReady()
 {
     bool ready = false;
+    MythDB *db;
 
     if ( !m_loggingTableExists )
         m_loggingTableExists = DBUtil::TableExists(m_handle.string);
 
-    if ( m_loggingTableExists && GetMythDB()->HaveValidDatabase() )
+    if ( m_loggingTableExists && (db = GetMythDB()) && db->HaveValidDatabase() )
         ready = true;
 
     return ready;
@@ -600,6 +601,17 @@ void logStop(void)
 {
     logThread.stop();
     logThread.wait();
+
+    QMutexLocker locker(&loggerListMutex);
+    QList<LoggerBase *>::iterator it;
+
+    for(it = loggerList.begin(); it != loggerList.end(); )
+    {
+        locker.unlock();
+        delete *it;
+        locker.relock();
+        it = loggerList.begin();
+    }
 }
 
 void threadRegister(QString name)