QA: Stop using "in" operator for node

The new configuration object for nodes will not support it anymore.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Helga Velroyen <helgav@google.com>

qa/qa_env.py

@@ -76,7 +76,7 @@ def TestIcmpPing():
   seccmd = [pingsecondary, "-e"]
   for i in nodes:
     pricmd.append(i["primary"])
-    if "secondary" in i:
+    if i.get("secondary"):
       seccmd.append(i["secondary"])
 
   pristr = utils.ShellQuoteArgs(pricmd)