Replaces local generate_uuid with common.utils

Reasons:
- generate_uuid is defined locally to use truncated uuid,
  without any specific need.
- This may result in similar UUIDs.
- Since tests work fine with usual common.utils.generate_uuid.

Reasons:
- Replaces local generate_uuid with generate_uuid from common.utils.

Change-Id: I5d46ba78169ce26c18c05160f02a8b01f88aca40
Closes-Bug: #1272685
Merge "Replaces local generate_uuid with common.utils"