test: move ethtool output parsing function to lib.

Signed-off-by: Emmanuel Roullit <emmanuel.roullit@gmail.com>
test: fix test function description header.

Signed-off-by: Emmanuel Roullit <emmanuel.roullit@gmail.com>
test: refactor expect output length test.

Signed-off-by: Emmanuel Roullit <emmanuel.roullit@gmail.com>
test: add interface coalease unit tests.

Signed-off-by: Emmanuel Roullit <emmanuel.roullit@gmail.com>
dabbad: fix interface coalesce getter.

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