network/wifi: use arguments in signal onDeviceEnabled

For an issue of network module of dde-session-daemon,
call IsDeviceEnabled() may cause dbus connection closed
if daemon initializing.

tower: https://tower.im/projects/8f19f0bf0e754f0b82ef2c24bc230973/todos/5e26d05f489548858edc4e77c79c411d/#e339f0d9b44d4e6eb7ff6824a1b080ff
Change-Id: Ie267a2e154ca86b260f4c23efc65bc4cd12e9768
Merge "network/wifi: use arguments in signal onDeviceEnabled" into release/2014.2