Guard pre-O apps from malicious startForegroundService()

Don't enforce the startForegroundService() requirement to transition to
foreground when the app hosting the service doesn't yet target the API
level at which this semantic was introduced.

Bug: 79377529
Test: manual (ApiDemos is pre-O)
Test: atest CtsAndroidAppTestCases
Change-Id: Ib0b970211d4ee6a86e22c89aff47b05403907ed5