nio: Add unit tests for setOption / getOption.

This also revealed an asymmetry in our APIs. The class defined
setOption but was missing a getOption method (inherited from
NetworkChannel).

bug: 27186457

(cherry-picked from commit dbbe65b6a81ad02bc3bd432f21dccce6c0242cdb)

Change-Id: I823af602b258bfc5f7508dc767af7f8dc4fcf537
4 files changed