StateMachine: remove final from SendMessage

Removed final from public sendMessage and sendMessageDelayed commands to
unblock unittest development.  This allows tests to verify calls to
sendMessage and sendMessageDelayed.

Also fixed one checkstyle error with import order.

BUG: 28593024
Change-Id: I26e02c3d75049d385ded7891c4fc9967273c27be
TEST: builds
TEST: runtest frameworks-wifi