The previous runAsShell calls adopted permissions spuriously. This
change fixes runAsShell to consistently adopt the correct permission
for the respective API call.
Also calls setEthernetEnabled() no matter what the current state is at
the end of the test (as there is no harm in doing so).
Test: TH
Flag: EXEMPT mainline
Change-Id: Ib11b889148213b160567cf0a3b9ea72b5b0c851e