SystemServer: reorder wifi services start

Start WifiService before other wifi-related services.
This is now possible since service dependencies were
removed from the WifiStateMachine constructor.

Bug: 34137732
Test: frameworks/opt/net/wifi/tests/wifitests/runtests.sh
Test: frameworks/base/wifi/tests/runtests.sh
Test: manually tested wifi connection
Test: manually checked for Wifi Direct peers
Change-Id: Iad4eb7053e60542d0be72208db53cf0f83004ae2