When vdev down flag is set, rx thread needs to flush the
pending frames in a fixed timeout value. Overall scheduler
timeout value is 10s, fixed timeout for each thread is 4s,
so if more than two threads timeout happens, scheduler timeout
may happen and lead to crash. Change to use adaptive timeout
for each thread to make overall threads wait time less than 10s.
Change-Id: If8acdaf1cac9d776e15d3020c8152101eae74a0c
CRs-Fixed: 2973947
2af4d0a937