Include square brackets in print_var dict terse format.

Including square brackets in the output makes it clear which fields are
dictionary key fields as opposed to variable names:

Previously, the output looked like this:

stack_dict:
  boot_stack:
    boot_stack[0]:    OBMC Reboot (off)

With the change it looks like this:

stack_dict:
  [boot_stack]:
    [boot_stack][0]:  OBMC Reboot (off)

Change-Id: I5ec260e6da022475d73185445f8e0013f40cabb3
Signed-off-by: Michael Walsh <micwalsh@us.ibm.com>
diff --git a/lib/gen_print.py b/lib/gen_print.py
index 52e41ba..39ae457 100755
--- a/lib/gen_print.py
+++ b/lib/gen_print.py
@@ -644,7 +644,7 @@
                     # turned off when processing integer dictionary values so
                     # it is not interpreted as a hex indicator.
                     loc_hex = not (type(value) is int)
-                    buffer += sprint_varx(key, value,
+                    buffer += sprint_varx("[" + key + "]", value,
                                           loc_hex, loc_col1_indent,
                                           loc_col1_width,
                                           loc_trailing_char)