Data Collect Plugin re-use

[rickycao-qy]

Pipeline works as following now:

1. provide a plugin-specific working dir for data-collect plugin. One data-collect plugin will download and maintain data in this working dir.

2. provide the same working dir to data-access plugin. Data-access plugin can also modify contents in this working directory.

This mechanism has the following problems that we hope data-collect plugin can make full use of this working directory. For example, they can reuse existing data, do some data cache, and optimize storage space. But since data-access plugin will also modify the same directory, the data-collect plugin will get lost

To solve this problem, I suggest we keep the current style for data-collect. Meanwhile, we provide a temp directory (job-specific) directory for data-access. This can be removed after the whole job is finished.