twister: tests: handler: fix incorrect timeout mock

There is clearly an issue with current timeout value
timeout into mocked_instance as this value is used only
once before this mock happen, so this mock is actually useless
and we always use default value. Fix that.

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Evgeniy Paltsev <PaltsevEvgeniy@gmail.com>