Reset unusable db connections (#6725)

When the management service detects a broken database connection, it didn't do anything about it. It already has code to reset the connection, but that doesn't get used. This change causes the connection to be reset after it's found to be unusable.

Fixes #6724 (see issue for repro steps)

Author: mrog

framework/db/src/main/java/com/cloud/utils/db/ConnectionConcierge.java

@@ -174,7 +174,7 @@ public String resetConnection(String name) {
 
             Connection conn = TransactionLegacy.getStandaloneConnection();
             if (conn == null) {
-                return "Unable to get anotehr db connection";
+                return "Unable to get another db connection";
             }
 
             concierge.reset(conn);
@@ -198,9 +198,13 @@ public String resetKeepAliveTask(int seconds) {
                 protected void runInContext() {
                     s_logger.trace("connection concierge keep alive task");
                     for (Map.Entry<String, ConnectionConcierge> entry : _conns.entrySet()) {
+                        String name = entry.getKey();
                         ConnectionConcierge concierge = entry.getValue();
                         if (concierge.keepAlive()) {
-                            testValidity(entry.getKey(), entry.getValue().conn());
+                            if (testValidity(name, concierge.conn()) != null) {
+                                s_logger.info("Resetting DB connection " + name);
+                                resetConnection(name);
+                            }
                         }
                     }
                 }