Don't offer "None" lock type for work profiles.

"None" doesn't make sense for work profiles because it makes
profile insecure even if primary user is secure. If the user
wants to get rid of separate challenge, it will be offered in
previous Settings page, "Use one lock", so this shouldn't cause
any confusion.

Test: atest tests/robotests/src/com/android/settings/password/ChooseLockGenericControllerTest.java
Test: manual, tried setting personal an work challenges from Settings and via Intent.
Bug: 33656033
Change-Id: I830b3e372c1fe200fc4e02d59e3c3805bac5f9bb