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.

log_manager/test/testorder.c

@@ -71,7 +71,7 @@ int main(int argc, char** argv)
     iterations = atoi(argv[1]);
     interval = atoi(argv[2]);
 
-    succp = skygw_logmanager_init(tmp, 1, optstr);
+    succp = skygw_logmanager_init(tmp, LOG_TARGET_FS, 1, optstr);
 
     if (!succp)
     {