fix checkContains

Change-Id: If0e0a97a02abba406bf9d1750c8d810526cc315a
diff --git a/src/com/mirantis/mk/Common.groovy b/src/com/mirantis/mk/Common.groovy
index c356da8..0b5e7ec 100644
--- a/src/com/mirantis/mk/Common.groovy
+++ b/src/com/mirantis/mk/Common.groovy
@@ -385,10 +385,10 @@
         if (v instanceof String && keyword instanceof String) {
             return v.toLowerCase().contains(keyword.toLowerCase())
         } else {
-            return False
+            return false
         }
 
     } else {
-        return False
+        return false
     }
 }