Only onboard when launched through front door.

When an app is using public API to take a photo, don't confuse the
user with the onboarding flow.

Test: cts-tradefed run commandAndExit cts-dev -m CtsProviderTestCases -t android.provider.cts.MediaStoreUiTest#testImageCapture
Bug: 62204676
Change-Id: Ie0de7b879302a5dd4bf941bf31b449bda95cfdf7