logger.c: Automatically add a newline to formats that don't have one

Scope tracing allows you to not specify a format string or variable,
in which case it just prints the indent, file, function, and line
number.  The trace output automatically adds a newline to the end
in this case.  If you also have debugging turned on for the module,
a debug message is also printed but the standard log functionality
which prints it doesn't add the newline so you have messages
that don't break correctly.

 * format_log_message_ap(), which is the common log
   message formatter for all channels, now adds a
   newline to the end of format strings that don't
   already have a newline.

ASTERISK-29209
Reported by: Alexander Traud

Change-Id: I994a7df27f88df343b7d19f3e81a4b562d9d41da