FRANKFURT (Reuters) – Germanys Siemens warned on Thursday that its energy business faced challenges in the coming quarters as it reported quarterly core profit that fell short of expectations. In the three months through June, operating profit from Siemenss four main businesses – Industry, Energy, Healthcare and Infrastructure Cities – rose 37 percent to 1.74 billion euros ($2.33 billion), missing analyst consensus of 1.83 billion in a Reuters poll. …