Comment 1 for bug 1602483

1. Same bug is on master, it was tried to solve different ways:
- modifying code to check BDM already exists (this can cause race conditions in BDM creation)
- adding unique uuid to BDM model (big change, it isn't finished yet)
2. Bug in downstream, possibly, can be solved in less strict conditions.

Idea:
- Check as early as possible volume is already linked.
- Or rollback changes after error in attachment.