* Ghani not inside building, but family members at home
* Taliban claims responsibility
* Kabul on high alert ahead of April 5 election (Adds Taliban statement, details)
By Hamid Shalizi and Samar Zaak
KABUL, March 25 (Reuters) - Suicide bombers attacked a building next to the house of Afghan presidential candidate Ashraf Ghani and engaged in a gun battle with security guards protecting...