autotest(wifi): Correct wait_for_service_states parameters.

The |wait_for_service_states| RPC call expects an array of strings as
the argument. Python's XML Rpc client converts single length tuple
into a string instead of array of string which causes a type
mismatch error on Brillo native proxy RPC server.
Correcting this parameter type to array instead of tuple in all usages.
This is already the case for some other tests like network_WiFi_ProfileBasic,
etc.

BUG=25323465
TEST=`test_that $host --board=$BOARD network_WiFi_ChannelHop` and
`test_that $host --board=$BOARD network_WiFi_RetryConnectHidden` on
dragonboard.

Change-Id: I89d9f2217c87fc76526375464c07d12227198d46