cbuildbot: make --all option clearer in --list

Add a note to the list output (like we have in the --help) that the
default --list is abbreviated and you need to use --all to see all.

BUG=chromium:492760
TEST=`cbuildbot -l` includes notice

Change-Id: Ie1ddaa50dc03673a6342c8649126dba17a341efa
Reviewed-on: https://chromium-review.googlesource.com/274940
Reviewed-by: Prathmesh Prabhu <pprabhu@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
diff --git a/scripts/cbuildbot.py b/scripts/cbuildbot.py
index 47f201b..cd823b5 100644
--- a/scripts/cbuildbot.py
+++ b/scripts/cbuildbot.py
@@ -70,7 +70,8 @@
             config_name)
 
   COLUMN_WIDTH = 45
-  print()
+  if not display_all:
+    print('Note: This is the common list; for all configs, use --all.')
   print('config'.ljust(COLUMN_WIDTH), 'description')
   print('------'.ljust(COLUMN_WIDTH), '-----------')
   config_names = site_config.keys()
@@ -81,8 +82,6 @@
       desc = desc if desc else ''
       print(name.ljust(COLUMN_WIDTH), desc)
 
-  print()
-
 
 def _ConfirmBuildRoot(buildroot):
   """Confirm with user the inferred buildroot, and mark it as confirmed."""