AnsibleRunnerClient: make 'mapper' a scoped object

There's no reason to keep the 'mapper' as part of 'AnsibleRunnerClient's
state - let's make it a local var.

Signed-off-by: Marcin Sobczyk <msobczyk@redhat.com>

backend/manager/modules/bll/src/main/java/org/ovirt/engine/core/common/utils/ansible/AnsibleRunnerClient.java

@@ -37,18 +37,12 @@
 @Singleton
 public class AnsibleRunnerClient {
     private static Logger log = LoggerFactory.getLogger(AnsibleRunnerClient.class);
-    private ObjectMapper mapper;
     private AnsibleRunnerLogger runnerLogger;
     private String lastEvent = "";
     private static final int POLL_INTERVAL = 3000;
     private AnsibleReturnValue returnValue;
 
     public AnsibleRunnerClient() {
-        this.mapper = JsonMapper
-                .builder()
-                .findAndAddModules()
-                .build()
-                .configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
         this.returnValue = new AnsibleReturnValue(AnsibleReturnCode.ERROR);
     }
 
@@ -253,6 +247,11 @@ public void runPlaybook(List<String> command, int timeout, String uuid) throws E
     protected String formatCommandVariables(Map<String, Object> variables, String playAction) {
         String result;
         try {
+            ObjectMapper mapper = JsonMapper
+                .builder()
+                .findAndAddModules()
+                .build()
+                .configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
             result = mapper.writeValueAsString(variables);
         } catch (IOException ex) {
             throw new AnsibleRunnerCallException("Failed to create host deploy variables mapper", ex);