Fix Windows build.

Now that 11c0f8e54cfc68d7d8efe34d10ad58ded687fcfa has landed, none of
the cases of the switch in |ssl3_ctrl| ever break and so the “return 1”
at the end of the function is unreachable. MSVC is unhappy about that.

Change-Id: I001dc63831ba60d93b622ac095297e2febc5f078