Increase thrift_framed_transport_size_in_mb from 15 to 256m

This is needed for Titan. We don't use thrift elsewhere, so this won't affect
anything else. We *could* introduce another variable here, but since it is not
going to differ between installations I think it's fine to just change the
default in the template.

Change-Id: I7bf356479ed0e58f4ceb610fade51331cd860eaf