* Iraqi PM stands up to Iran's Soleimani on war operations * Abadi puts internal reconciliation, detente with Saudi on agenda * Grand Ayatollah said to back Abadi's move to streamline cabinet * Oil price collapse, Iran's allies main challenge to Abadi's rule By Maher Chmaytelli BAGHDAD, Feb 21 (Reuters)- - As fighting in Iraq raged last summer, Iranian Major-General Qassem Soleimani came across unexpected opposition to his plans to defeat Islamic State. Soleimani is the commander of Iran's al-Quds brigade and has been a key figure in the fight against the Sunni Islamist group in Iraq.