Merge release branch 4.9 to master

* 4.9:
  CLOUDSTACK-9460: For long running transactions, if the connection is timed out by the mysql server then refresh it

Author: jburwell

framework/db/src/com/cloud/utils/db/TransactionLegacy.java

@@ -168,14 +168,24 @@ public static TransactionLegacy open(final String name, final short databaseId,
                 isNew = true;
             }
         }
-
+        txn.checkConnection();
         txn.takeOver(name, false);
         if (isNew) {
             s_mbean.addTransaction(txn);
         }
         return txn;
     }
 
+    public void checkConnection() {
+        try {
+            if (_conn != null && !_conn.isValid(3)) {
+                _conn = null;
+            }
+        } catch (SQLException e) {
+            _conn = null;
+        }
+    }
+
     protected StackElement peekInStack(Object obj) {
         final Iterator<StackElement> it = _stack.iterator();
         while (it.hasNext()) {