Lock Private space at the end of PS setup.

This change is to call UserManager requestQuietModeEnabled() API at the
end of PS setup to enable quitemode for private space.

Bug: 313652502
Test: atest PrivateSpaceMaintainerTest
Verify Private space is locked state after private space setup completion.

Change-Id: I1d863f6d51ffa4bb58318696603905d35c3109b6