[Network]Fix startup net connect delay

    When system startup, CheeseBrowser receive network
connected action, this time, the network traffic can't
transfer data, need wait some time.But not sure how long
the time is.To solve the problem, we add a parameter to
preference.So user can manual configure the wait time.

Signed-off-by: Ethan Shan <shan0xiao0xi@gmail.com>