Slightly change the "pre-N" so it's CTS-friendly.

Right now, the value of VERSION_CODES.N is 10000, but I'm writing
a caller app with target SDK level 24 for CTS, and the previous
logic didn't work for it.

Bug 25506830

Change-Id: I73613f30b437fb19406736f897d01d59b1f84c9d