Add explicit check/update to preprocessing step ordering in LLD

Steps to reproduce:

1. Create template with discovery rule
2. Create three item prototypes in this discovery rule. All of these item prototypes should have two preprocessing steps.
3. Create host and link this template to it.
4. Perform a discovery
5. Add new preprocessing step (third) to templated item prototype (for the one that is parent to item prototype with highest ID)
6. Perform discovery second time

Result:

• newly added preprocessing step in discovered item is first.
• preprocessing steps in item prototype are in correct order.

Expected:

• preprocessing steps in discovered item should be in same order, as in item prototype.