How to Disable Screen Lock

Problem
- How to disable Pattern Screen Lock
- "Disabled by Administrator, encryption policy, or credential ...
- Can't disable screen lock
- Can't disable pattern screen lock

Case Study (Screen lock)
None (Grayed out) Disabled by administrator, encryption policy, or credential storage. 
Slide (Grayed out) Disabled by administrator, encryption policy, or credential storage.
Face Unlock (Grayed out) Disabled by administrator, encryption policy, or credential storage.
Pattern (Enabled)
PIN (Enabled)
Password (Enabled)

Solution
Go to SETTINGS > Security > Clear credentials (last item) and then go to Screen lock