test: reinforce patterns to grep ethtool output.

Signed-off-by: Emmanuel Roullit <emmanuel.roullit@gmail.com>
test: 'usec' takes an 's' in ethtool output.

Signed-off-by: Emmanuel Roullit <emmanuel.roullit@gmail.com>
test: check for rx/tx adaptive coalescing.

Signed-off-by: Emmanuel Roullit <emmanuel.roullit@gmail.com>
test: check rate sample & stats block values.

Signed-off-by: Emmanuel Roullit <emmanuel.roullit@gmail.com>