Fixed ommited http module include

Change-Id: Id0fedc52b6501c9dadb88ba1359a6871aa72e86c
diff --git a/src/com/mirantis/mk/salt.groovy b/src/com/mirantis/mk/salt.groovy
index df6a033..30b2f16 100644
--- a/src/com/mirantis/mk/salt.groovy
+++ b/src/com/mirantis/mk/salt.groovy
@@ -54,6 +54,8 @@
  * @param kwargs   Additional key-value arguments to function
  */
 def runSaltCommand(master, client, target, function, args = null, kwargs = null) {
+    def http = new com.mirantis.mk.http()
+
     data = [
         'tgt': target.expression,
         'fun': function,