* Ghani not in building, but family members at home
* Taliban claims responsibility
* Kabul on high alert ahead of April 5 election
By Hamid Shalizi and Maria Golovnina
KABUL, March 25 (Reuters) - Suicide bombers and gunmen in Afghanistan attacked an election commission office beside the home of presidential candidate Ashraf Ghani on Tuesday, rattling nerves in the Afghan capital less ...