Require ProtobufProcess message handlers to take the sender explicitly.

Review: https://reviews.apache.org/r/14900
Updated users of ProtobufProcess::from.

Review: https://reviews.apache.org/r/14901
Removed logging to /tmp when --log_dir is ommitted.

The current intialization of glog creates log files in /tmp even when
the log_dir command argument is not passed. Setting FLAGS_logtostderr
to true disables all log file creation/writes.

From: Yuval Pavel Zholkover <paulzhol@gmail.com>
Review: https://reviews.apache.org/r/14800