Security bug fix: Prevent USB data changes for non-owner users during lockdown mode.

The onStrongAuthRequiredChanged callback now only affects USB data for non-guest users. This prevents USB data from being enabled for guest users when the device enters lockdown mode.

Bug: 466379326
Flag: EXEMPT bugfix
Test: manual, UsbServiceTest
(cherry picked from commit d1d84790170ed14a43e94916b2a72705a28ed120)
Cherrypick-From: https://googleplex-android-review.googlesource.com/q/commit:fea130396d83cf4fcf931880fe86acc384ecfb20
Merged-In: Ifa549103a0f454921334aad5687653088609da2d
Change-Id: Ifa549103a0f454921334aad5687653088609da2d