Add script to use tempest-lib files in tempest

As many files have been migrated to tempest-lib and
we need to remove those from tempest and make use of lib.

That is easy work but doing it manually takes times.
Automating that process same way it was done for migrating files to lib.

This commit adds new script use_tempest_lib for using the files
from tempest-lib.

In short this script does below steps-

- Get the latest tempest commit-id of file.
- Clone the tempest-lib and fetch the migration commit information
  - Get the tempest commit-id of file which was migrated to lib.
- Check Diff of both (latest commit-id and migrated commit-id).
- If both are same then delete those files from tempest and edit import of
  those file using tempest-lib file.

Sample - Id28c615534235c345e31b895a77a53ceac4af1a4

Change-Id: I8177f47113b6ab9b23af8ff86b87bb946ad549ad
1 file changed