A couple of years ago commit a4f50e3b introduced a new checkstyle validation in oVirt Engine that enforces the order of the imports since some of the developers did not use the standards from the Engine code format and this caused a situation where some commits included aside for the actual code also a reformat of the imports that was unrelated to the patch.
After the validation was added the situation got better but there were still no 100% alignment since the Engine code format also defines that there should be that there should be a blank line between the different import groups and this was not enforced, a fact that caused some patches to add lines and some remove lines between the imports.

Today I've merged commit bf298fed that fixes all the imports as per the project standard and commit 1c6b710 that adds a checkstyle validation that enforces this change so note that from now on you should maintain that.

You can add the code format which is located in Engine root under config/engine-code-format.xml to your IDE to have the imports arranged automatically.