Fix BMC network config test suite

Changes:
   - Modified variable name instead HTTP_OK.

Tested:
   - Ran and tested on BMC Environment.

Change-Id: I13bd622454f2bb0ffff1c087c2547fd5d5645546
Signed-off-by: Anvesh-Kumar_Rayankula <anvesh.kumar.rayankula@ibm.com>
diff --git a/lib/bmc_network_utils.robot b/lib/bmc_network_utils.robot
index f43aece..3d32fbd 100644
--- a/lib/bmc_network_utils.robot
+++ b/lib/bmc_network_utils.robot
@@ -912,4 +912,4 @@
     Sleep  3s
 
     # Check if newly added DNS server is configured on BMC.
-    CLI Get and Verify Name Servers  ${static_name_servers}  ${HTTP_OK}
+    CLI Get and Verify Name Servers  ${static_name_servers}  ${valid_status_codes}