test: modify rx/tx adaptive settings if supported.

Signed-off-by: Emmanuel Roullit <emmanuel.roullit@gmail.com>
test: add packet rate & stats block modify tests.

Signed-off-by: Emmanuel Roullit <emmanuel.roullit@gmail.com>
test: properly modify interface pause settings.

Signed-off-by: Emmanuel Roullit <emmanuel.roullit@gmail.com>
test: add interface pause modify checks.

Signed-off-by: Emmanuel Roullit <emmanuel.roullit@gmail.com>
dabba: trim '-pause' from rx/tx pause switches.

Users invoking this command might already know that it will influence
pause settings. No need to repeat that in the switch names.

Signed-off-by: Emmanuel Roullit <emmanuel.roullit@gmail.com>
test: modify pause settings first, restore later.

The settings received by autonegotiation take precedence over the user
settings. To perform correct tests, the interface pause autonegotiation
must be deactivated first.

When all modifications are done, they are reverted afterwards.

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