[artifactory] Always set 'Use credentials' flag

    Formula supports credential-based artifactory authorization only.
    So need to set `Use the Credentials Plugin` parameter
    unconditionally

    Closes-PROD: https://mirantis.jira.com/browse/PROD-21302

Change-Id: I6218ab89e2347614d1c15ee48a6297e392341cee
diff --git a/_states/jenkins_artifactory.py b/_states/jenkins_artifactory.py
index daccc2e..d88b84a 100644
--- a/_states/jenkins_artifactory.py
+++ b/_states/jenkins_artifactory.py
@@ -8,6 +8,9 @@
 import org.jfrog.hudson.*
 def inst = Jenkins.getInstance()
 def desc = inst.getDescriptor("org.jfrog.hudson.ArtifactoryBuilder")
+if (! desc.useCredentialsPlugin ) {
+    desc.useCredentialsPlugin = true
+}
 // empty artifactory servers is not empty list but null, but find can be called on null
 def server =  desc.getArtifactoryServers().find{it -> it.name.equals("${name}")}
 if(server &&