Fixed missing interpolation char in jenkins_plugin salt state

Change-Id: I85a7f2c086b2ddf35a2a92408263fda1a861907d
diff --git a/_states/jenkins_plugin.py b/_states/jenkins_plugin.py
index d9fe8e9..0f80d51 100644
--- a/_states/jenkins_plugin.py
+++ b/_states/jenkins_plugin.py
@@ -38,7 +38,7 @@
 }
 if (installed) {
   instance.save()
-  if({restart}){
+  if(${restart}){
       instance.doSafeRestart()
    }
   print("INSTALLED")