Test scenario 1:
1. Revert snapshot "ready_with_3_slaves"
2. Create env with 3 controller nodes and 1 compute+cinder node
3. Provision nodes
4. Upload two simple graphs
5. Make snapshots for next tests and resume snapshot
6. Execute graphs
7. Check that graph tasks was executed and
finished without any errors
8. Check the created by graph tasks file
Test scenario 2:
1. Revert snapshot "extension_graph_prepare_env"
2. Execute graphs via API
3. Check that graph tasks was executed and
finished without any errors
4. Check the created by graph tasks file
Change-Id: I45849d680c1224771ac8db61827ac56950c903f4
Closes bug: 1619638
Blueprint: graph-concept-extension
894f6883be