Edit Deployment (and DC) form doesn't enable Save button when changing strategy type

Description of problem:
When the user edits a deployment and switches (just) the rollout "Strategy type" the form couldn't be saved because the Save button stays disabled.

Version-Release number of selected component (if applicable):
4.13

How reproducible:
Always

Steps to Reproduce:

1. Import an application from git
2. Select action "Edit Deployment"
3. Change the "Strategy type" value

Actual results:
Save button stays disabled

Expected results:
Save button should enable when changing a value (that doesn't make the form state invalid)

Additional info: