fix if condition in salt models testing

Change-Id: I9a12b00aeec805cea1b2b24a70ac1f9cf345860f
diff --git a/src/com/mirantis/mk/SaltModelTesting.groovy b/src/com/mirantis/mk/SaltModelTesting.groovy
index 7c478dd..9ab54a1 100644
--- a/src/com/mirantis/mk/SaltModelTesting.groovy
+++ b/src/com/mirantis/mk/SaltModelTesting.groovy
@@ -22,8 +22,9 @@
     imageFound = false
   }
 
-  if (extraFormulas == "")
+  if (extraFormulas == "") {
     extraFormulas = "linux"
+  }
 
   img.inside("-u root:root --hostname=${masterName}") {
     wrap([$class: 'AnsiColorBuildWrapper']) {