app/testpmd: fix timeout in Rx queue flushing

app/testpmd: fix timeout in Rx queue flushing

When testpmd is run, the application would hang on the second time
that "start" is executed. This is because the timer limit would get
multiplied to an unreachably high number.

At the start of flush_fwd_rx_queues(), the timer limit now resets
to stop it from getting to this high number.

The timer has been made local for this function.

Fixes: f487715f36f5 ("app/testpmd: add timeout in Rx queue flushing")

Signed-off-by: James Poole <james.g.poole@intel.com>
Acked-by: Ferruh Yigit <ferruh.yigit@intel.com>