Call of IBP are exclusive. That is why original watching mechanism
for log provisioning does not work. Now we run parallel thread
for reporting progress about IBP
Also:
* add and update tests;
* fix problem with non-breaking provisioning.
Change-Id: Ib3b6d79bedbf96281ef4645fcc9e78e4b4aa02d9
Implements: blueprint ibp-build-ubuntu-images
Closes-Bug: #1383748
19b5fbdf00