Revert "add "Turn Wi-Fi off" action to the "open networks available" notification"

This reverts commit 88850b725fe42b432d9c90836ca2f78b63693804.
ConnectivtyService : Execute connectivityCheck in thread pool

Since this async task takes long when doing things like waiting for
network connectivity...etc, rather than holding up the single executor
of async task for the framework (app_process), run it on a thread from
the pool so other tasks can execute in parallel.

Change-Id: I7b88a4837c7e117ef47014a20c57f828b811edfb