By rewriting a few stanza's to give the compiler more flexibility in
order of operations, reduce code size by about 1kb.

* Reference discussion: https://github.com/grpc/grpc/pull/4108#discussion-diff-44494393

- server logger.level = WARN
- client logger.level = INFO

- truncates the server debug log entries to make that readable

This fixes the current ruby server interop test flakiness.

- The interop tests recently changed so that clients access servers in
parallel, meaning that the interop servers handle multiple rpcs at once,
which is how this bug became visible

- since this change, tests run against the ruby interop server have
failed sporadically

- the problem was that the block in #loop_handle_server_calls that is
  passed to the thread pool referenced a var in an enclosing block,
  which resulted in requests being processed by the wrong handler

- this fix ensures that the block to be run on the thread pool thread
  does not have any references to vars in the enclosing block

Fixes an omission from earlier PRs that adds support metadata.