The provisions of Sections 41-29-301 through 41-29-311 restricting the possessing and having control of narcotic drugs shall not apply to common carriers or to warehousemen, while engaged in lawful transporting or storing such drugs, or to any employee of the same acting within the scope of his employment; or to public officers or employees in the performance of their official duties requiring possession or control of narcotic drugs; or to temporary incidental possession by employees or agents of persons lawfully entitled to possession, or by persons whose possession is for the purpose of aiding public officers in performing their official duties.