Tiny fix on R-CNN Fine-tuning PASCAL example (to dev)

This PR is a tiny fix on R-CNN Fine-tuning PASCAL example, which fix the directory names in the solver file.

When deploying caffe on a new machine in my university, I run the fine-tuning R-CNN example as a check to see if training works correctly. However, I found I could not launch this example as the path in the solver is inconsistent with the directory name.

In #1117 I made a mistake by making a PR against master branch. This is another PR to merge it into dev. I apologize for the mistake.