Refactor: scheduler: remove redundant code

unpack_rsc_op() doesn't need to map status PCMK_LRM_OP_ERROR to
PCMK_LRM_OP_DONE because it explicitly looks for both when it uses status

check_operation_expiry() doesn't need to check that failure_timeout is positive
when expired is true, because expired can be true only if failure_timeout is
positive

check_action_definition() doesn't need to check whether task is stop because
it cannot be called for stops

check_actions_for() doesn't need to check whether a status operation is a probe
because it also checks for recurring operations in the same place