test: use official repo instead of third pard repo

Author: rainingmaster

.travis.yml

@@ -83,7 +83,7 @@ install:
   - git clone https://github.com/openresty/rds-json-nginx-module.git ../rds-json-nginx-module
   - git clone https://github.com/openresty/srcache-nginx-module.git ../srcache-nginx-module
   - git clone https://github.com/openresty/redis2-nginx-module.git ../redis2-nginx-module
-  - git clone -b exit_worker https://github.com/rainingmaster/lua-resty-core.git ../lua-resty-core
+  - git clone https://github.com/openresty/lua-resty-core.git ../lua-resty-core
   - git clone https://github.com/openresty/lua-resty-lrucache.git ../lua-resty-lrucache
   - git clone https://github.com/openresty/lua-resty-mysql.git ../lua-resty-mysql
   - git clone https://github.com/openresty/lua-resty-string.git ../lua-resty-string