<fix>[core,kvm]: fix SSH session leak in CallBackNetworkChecker and KVMHost

1. CallBackNetworkChecker.stopAnsible() creates Ssh object but never
   closes it, leaking JSch Session thread on every call.
2. KVMHost "check-host-is-taken-over" flow has the same pattern.

When a host continuously fails reconnect (e.g. sharedblock VG error),
each reconnect cycle leaks 1-2 SSH sessions. Over days this exhausts
heap memory (18000+ threads observed) causing MN OOM and Unknown status.

Fix: add finally { ssh.close() } to both code paths.

Resolves: ZSTAC-83305
Resolves: ZSTAC-82731

Change-Id: I786e766e79776d6b7a75786d776278696c76666f

Author: MaJin1996

core/src/main/java/org/zstack/core/ansible/CallBackNetworkChecker.java

@@ -72,6 +72,8 @@ public ErrorCode stopAnsible() {
             return useNcatAndNmapToTestConnection(ssh);
         } catch (SshException e) {
             return operr(ORG_ZSTACK_CORE_ANSIBLE_10004, e.getMessage());
+        } finally {
+            ssh.close();
         }
     }
 

plugin/kvm/src/main/java/org/zstack/kvm/KVMHost.java

@@ -5573,10 +5573,10 @@ public boolean skip(Map data) {
 
                     @Override
                     public void run(FlowTrigger trigger, Map data) {
+                        Ssh ssh = new Ssh().setUsername(getSelf().getUsername())
+                                .setPassword(getSelf().getPassword()).setPort(getSelf().getPort())
+                                .setHostname(getSelf().getManagementIp());
                         try {
-                            Ssh ssh = new Ssh().setUsername(getSelf().getUsername())
-                                    .setPassword(getSelf().getPassword()).setPort(getSelf().getPort())
-                                    .setHostname(getSelf().getManagementIp());
                             ssh.command(String.format("grep -i ^uuid %s | sed 's/uuid://g'", hostTakeOverFlagPath));
                             SshResult hostRet = ssh.run();
                             if (hostRet.isSshFailure() || hostRet.getReturnCode() != 0) {
@@ -5625,6 +5625,8 @@ public void run(FlowTrigger trigger, Map data) {
                             logger.warn(e.getMessage(), e);
                             trigger.next();
                             return;
+                        } finally {
+                            ssh.close();
                         }
                     }
                 });