MDL-45641 event: Removed multiple user_updated event trigger

user_updated event was being triggred while
setting password, which is not correct. It now
trigger user_password_updated event. Few more
modifications done:
1. Correct event is being triggred.
2. Event is only triggred when password is chnaged.
3. Password is updated via single api.
4. Updated unit test
MDL-45641 event: Manually trigger event where needed.

Some places, user_created_user and user_updated_user
events should be triggred after profile data is saved.
MDL-45641 event: Ldap user_signup unit test added