Settings unexpectedly open after turning work profile on

ConfirmDeviceCredentialActivity doesn't set a taskAffinity, so the
default taskAffinity is the package name. That's why Settings
unexpectedly open after users turn work profile on. We specified an
unique name to taskAffinity to avoid launching Settings activity.

Fixes: 129330530
Test: turn work profile off then turn it on, repeat
Change-Id: I1f71c3d1bb37a09a6393fae4c01bc9b18cab49a8