config.c: fix memory leak in convert_controller_versions()

config.c: fix memory leak in convert_controller_versions()

Fix memory leak warning in convert_controller_versions(), reported by
Coverity tool:

CID 313911 (#1 of 1): Resource leak (RESOURCE_LEAK)9. leaked_storage:
Variable cgrp_cpy going out of scope leaks the storage it points to.

struct cgroup cgrp_cpy was not free'd in the success path, fix it.

Signed-off-by: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Signed-off-by: Tom Hromatka <tom.hromatka@oracle.com>