Pretend _CDB_UserQuotaInBytes has to stay in public

Fixes run of the testsuite in the pre-extension model

scripts-available/CDB_Quota.sql

@@ -36,7 +36,7 @@ BEGIN
   IF dice < pbfact THEN
     RAISE DEBUG 'Checking quota on table % (dice:%, needed:<%)', TG_RELID::text, dice, pbfact;
     BEGIN
-      qmax := cartodb._CDB_UserQuotaInBytes();
+      qmax := public._CDB_UserQuotaInBytes();
     EXCEPTION WHEN undefined_function THEN
       RAISE WARNING 'Missing _CDB_UserQuotaInBytes(), assuming no quota';
       qmax := 0;
@@ -67,12 +67,12 @@ DECLARE
   sql text;
 BEGIN
   BEGIN
-    current_quota := cartodb._CDB_UserQuotaInBytes();
+    current_quota := public._CDB_UserQuotaInBytes();
   EXCEPTION WHEN undefined_function THEN
     current_quota := 0;
   END;
 
-  sql := 'CREATE OR REPLACE FUNCTION cartodb._CDB_UserQuotaInBytes() '
+  sql := 'CREATE OR REPLACE FUNCTION public._CDB_UserQuotaInBytes() '
     || 'RETURNS int8 AS $X$ SELECT ' || bytes
     || '::int8 $X$ LANGUAGE sql IMMUTABLE';
   EXECUTE sql;