Logging target must be explicitly defined.

Whether the log-file should be written to the filesystem or to
shared memory must now be explicitly defined when calling
skygw_logmanager_init() (instead of passing that via the argc/argv
construct).

Also, the meaning of '-l' when invoking maxscale has been changed.

Earlier -l [file|shm] specified whether the trace and debug logs
should be written to shared memory (while the error and message
logs always were written to the filesystem) and the _default_
was to write them to shared memory.

Now, with only one file, '-l' has still the same meaning, but it
decides whether the one and only logfile should be written to shared
memory, or the filesystem and the _default_ is to write it to the
filesystem.

server/include/test_utils.h

@@ -20,7 +20,7 @@ void init_test_env(char *path)
             NULL
         };
 
-    skygw_logmanager_init(logdir, argc, argv);
+    skygw_logmanager_init(logdir, LOG_TARGET_DEFAULT, argc, argv);
     poll_init();
     hkinit();
 }