* Iran's nuclear work is abiding concern for Gulf Arabs * Risk of summit boycott drove GCC reconciliation * Gulf dominant power Saudi pushed for end to row By William Maclean and Amena Bakr DUBAI/DOHA, **v 19 (Reuters) - Gulf Arab states have shelved a bitter row among themselves, hoping to repair an alliance that has been sorely tested by chaos in the Middle East and the prospect of an Iranian nuclear deal that could tilt the regional balance of power towards their old foe Tehran. ...