MOGADISHU—Somali lawmakers voted unanimously on Saturday to cancel a two-year presidential term extension they had approved last month, after clashes in the capital Mogadishu between factions of the security forces, which are divided over the issue. In a speech following the vote in the lower house of parliament, Prime Minister Mohamed Hussein Roble ordered the army to return to barracks and urged politicians to avoid inciting violence. The political crisis has raised fears that al Qaeda-linked al Shabaab terrorists could exploit a security vacuum if state forces split along clan lines and turn on each other. The group has taken over at least one Somali town in the past week as heavily armed fighters moved from the countryside into the capital city. President Mohamed Abdullahi Mohamed’s attempt to extend his term has also angered foreign donors, who have backed his government in an attempt to bring stability to Somalia after …