Fix syntax warning

Signed-off-by: Michael Shepos <shepos@us.ibm.com>
Change-Id: I76662ba1830484a316934011482eb6fb485c10fc
diff --git a/lib/bmc_ssh_utils.py b/lib/bmc_ssh_utils.py
index 9dc3bd4..c82788f 100755
--- a/lib/bmc_ssh_utils.py
+++ b/lib/bmc_ssh_utils.py
@@ -106,9 +106,9 @@
     # Get global OS variable values.
     if os_host == "":
         os_host = BuiltIn().get_variable_value("${OS_HOST}", default="")
-    if os_username is "":
+    if os_username == "":
         os_username = BuiltIn().get_variable_value("${OS_USERNAME}", default="")
-    if os_password is "":
+    if os_password == "":
         os_password = BuiltIn().get_variable_value("${OS_PASSWORD}", default="")
 
     if not gv.valid_value(os_host):