Make GLIF theme default for confirm lock screen

Use GLIF theme as the default for confirm lock screen, even for
"external" launches of the screen. Renamed the theme from "internal"
to "normal" to reflect this change.
Dark theme code will be cleaned up later.

Test: Existing tests pass
Bug: 62573742
Change-Id: I86958eb3a440d7274807f1cf453c3e53c16c23e7