Treat background mic/camera normally

Since the addition of background mic/camera, the foreground mode now
takes the mode MODE_FOREGROUND so now we don't need to treat
MODE_ALLOWED specially for microphone and camera.

Test: Try bg camera/mic access from fg/bg && with both levels of access
Bug: 158311343
Change-Id: I17b5cbfe6644bcbfc9c295487ca41482113562d9