s/database/distributed<database>/ everywhere.
Use simple distribution rules: writes are broadcast, reads are local.
This causes tremendous data duplication, but will change soon.
The code attempts to use scattered_message::append_static() to gain zero
copy, claiming that _output protects the data's lifetime, but that's a
false claim - it will remain in the transmit queue waiting for an ACK
while we process (and respond to) the next request.
Fix by just writing the output naturally. We may zero-copy support later,
though it is dubious it will help thrift, as the code is full of copies
and atomics.
