handle supplicant stop after child states exit

When a user explicitly disables wifi, wait on the supplicant shut down until after
all child states have handled exit - this avoids time outs due to communicating with
supplicant after breaking the socket connection

Bug: 4052161

Change-Id: Iec5bb3e14a2df4a8a12de8bb81d9c10aeb992ad4
1 file changed