logger: allow to log using tcp transport protocol

This commit fixes error in usage() text, which claimed TCP is default
transport protocol.  That was not true, and neither it should be.  The
syslog messages has traditionally been sent using UDP.  The logger
remains using UDP as first transport, but if it fails (can that be
determined even in theory?) TCP connection is attempted.  Fallback TCP
connection is made to syslog-conn port, which is likely best guess as
there is not well known syslog port.

Signed-off-by: Sami Kerola <kerolasa@iki.fi>