Increase heat's default max_template_size

devstack has a small 10k max template size.  This is too small for
many templates that may be used during development.  Thus, we need
to change this and devstack to a larger value.

Change-Id: I474c7cbc196a4e94ba67cab4e2ca2263dc902e26

tempest/config.py

@@ -410,7 +410,7 @@ OrchestrationGroup = [
                default=None,
                help="Name of existing keypair to launch servers with."),
     cfg.IntOpt('max_template_size',
-               default=10240,
+               default=32768,
                help="Value must match heat configuration of the same name."),
 ]