* Former rebel proxy wins 30 out of 38 seats
* Rajapaksa suffers worst defeat since he assumed office
* Victory could reignite calls for autonomy (Adds comment from chief candidate)
By Shihar Aneez
JAFFNA, Sri Lanka, Sept 22 (Reuters) - Sri Lanka's main ethnic minority Tamil party secured a landslide victory in a provincial poll that has threatened to rekindle animosity between the ...