Fix for enormous progress bar rising of deployment task

Weight for node deletion subtask of deployment supertask in
ApplyChangesTaskManager added. New integration tests added. Some
refactoring to TaskHelper performed: formula that calculate progress for
supertask has been moved to separate class method.

Change-Id: I2143f9999320c66b49940844d5b1b7a7f5e2a77c
Closes-Bug: #1286124
Merge "Fix for enormous progress bar rising of deployment task"