Failure to print "<blank>" when asked.

lib/gen_print.py:
  - sprint_varx:  Not printing "<blank>" when var_value is "".  Fixed.

Change-Id: Ifdf20d1fa803b23699371641d5c618f77d172b7c
Signed-off-by: Michael Walsh <micwalsh@us.ibm.com>
diff --git a/lib/gen_print.py b/lib/gen_print.py
index ad06757..79e70d6 100755
--- a/lib/gen_print.py
+++ b/lib/gen_print.py
@@ -501,7 +501,7 @@
         if hex:
             if type(var_value) not in (int, long):
                 value_format = "%s"
-                if var_value is "":
+                if var_value == "":
                     var_value = "<blank>"
             else:
                 value_format = "0x%08x"