Use absolute path for the values of get_status (fix #634)

Fix #634.

The only source of relative paths is command line argument, so I canonicalized right after parsing it.

These arguments are affected:

```
  -d, --datadir                 directory to save and load models (string [=/tmp])
  -l, --logdir                  directory to output logs (instead of stderr) (string [=])
  -f, --configpath              config option need to specify json file when standalone mode (without ZK mode) (string [=])
  -m, --model_file              model data to load at startup (string [=])
```