engine: AsyncTaskManager - restart fix part 1 (Logic)

The following fix should change a current behaviour which is:
During creation child command which is asynchronious a parameters of parent
command are saved in DB (this ok), but parameters of parent comand also contains a list
of parameters of child commands (sic!).
So a first child command created we save a parent command with list of one command,
second command created list with two commands and etc...
After a restart and random child is choosen, so we have a random number of child parameters.
By the way , if list of child parameters is updated after saving a task to db, we will never have a correct list
(Example can be seen in one of the next patches)
Solution, save to DB parent parameters and appropriate child command parameter, during endAction() bnuild a list
of parameters.
One of the known bugs (a lot of unknown): During preview on vm after all task are send to host, perform restart.
All task are send, all task finished successfully, but disk still left in status Locked and the number of disks is
random
Benefits:
1. Bug is solved
2. Reduced serialization and desirialization (by current situation we have O(n^2) serialization/deserialization operations)
3. Most of the logic moved to the same place, no need to copy paste it all over a project
4. No need to make work arounds all over a project

What is still not solved:
If we will fail in the middle of task creation, we will not know if all task that we have that all tak that we wanted to start,
the fix is easy and will be send soon

Change-Id: I06507f537b2de0dc358a59aa27e62cbb042ccbb1
Signed-off-by: Michael Kublin <mkublin@redhat.com>
engine: AsyncTaskManager - fix restart part 1 (DB)

The following patch contains a changes for DB schema which is required in order to solve
a problem.
The changes are: added a new two collums to async_task table.
Those columns are respresenting a parameters of command which is associated with task

Change-Id: I3beb5c4a675c567abdf789f40c26fd9fa0a1fb4d
Signed-off-by: Michael Kublin <mkublin@redhat.com>
engine: AsyncTaskManager - fix restart part 1 (Clean ups)

The following patch contains a clean ups, the following code is not needed anymore
after introducing a fix.
Also at some classes like AddVmFromTemplateCommand we can see that child parameters are
added to list only after persist of the task to DB, so after a restart we will never have
a task which have a parent parameters with all list of child parameters (sic!)

Change-Id: I2c8c26b79df08a139c6bd19b28dd376ba69829ca
Signed-off-by: Michael Kublin <mkublin@redhat.com>