server: Loglevel adjustments for shutdown path.

server: Loglevel adjustments for shutdown path.

The log output of the server is rather verbose with respect to
shutdown messages. These not only occur when the server exits but
also in command handler context each time a command is executed.

This patch quietens these messages in two ways. For some messages we
simply reduce the log level. For others we print the message only in
server context, i.e. when process_is_command_handler() returns false.