Fixed debugging output

Change-Id: I0a4e7c73561c95345cb30031aab7b441aea42f00
diff --git a/src/com/mirantis/mk/Common.groovy b/src/com/mirantis/mk/Common.groovy
index 1c958b5..daf9f38 100644
--- a/src/com/mirantis/mk/Common.groovy
+++ b/src/com/mirantis/mk/Common.groovy
@@ -145,7 +145,7 @@
  */
 def debugMsg(msg, color = true){
     // if debug property exists on env, debug is enabled
-    if(env.getEnvironment().containsKey('DEBUG')){
+    if(env.getEnvironment().containsKey('DEBUG') && env['DEBUG'] == "true"){
         printMsg("[DEBUG] ${msg}", "red")
     }
 }