[docker-image-scanner] Fix var name

Jobs fails with:
  "The current scope already contains a variable of the name issueJSON"

Change-Id: Icde8d1e0a8d3f876076bc18fa7503b74645d7054
Related-PROD: https://mirantis.jira.com/browse/RE-274
diff --git a/src/com/mirantis/mk/DockerImageScanner.groovy b/src/com/mirantis/mk/DockerImageScanner.groovy
index 1be81a9..9083687 100644
--- a/src/com/mirantis/mk/DockerImageScanner.groovy
+++ b/src/com/mirantis/mk/DockerImageScanner.groovy
@@ -201,9 +201,9 @@
 
             def team_assignee = getTeam(image_key)
 
-            def issueJSON = new JsonSlurper().parseText('{"fields": {}}')
+            def basicIssueJSON = new JsonSlurper().parseText('{"fields": {}}')
 
-            issueJSON['fields'] = [
+            basicIssueJSON['fields'] = [
                 key:"${jiraNamespace}",
                 summary:"${jira_summary}",
                 description:"${jira_description}",
@@ -216,10 +216,10 @@
                 ]
             ]
             if (jiraNamespace == 'PRODX') {
-                issueJSON['fields']['customfield_19000'] = [value:"${team_assignee}"]
-                issueJSON['fields']['versions'] = [["name": "Backlog"]]
+                basicIssueJSON['fields']['customfield_19000'] = [value:"${team_assignee}"]
+                basicIssueJSON['fields']['versions'] = [["name": "Backlog"]]
             }
-            def post_issue_json = JsonOutput.toJson(issueJSON)
+            def post_issue_json = JsonOutput.toJson(basicIssueJSON)
             def post_comment_json = """
 {
     "body": "${jira_description}"