tools/cgxget: de-allocate cg_convert_list[] in convert_cgroup()

tools/cgxget: de-allocate cg_convert_list[] in convert_cgroup()

The commit 66799b867c7 (tools/cgxget: fix the resource leak in
convert_cgroup()), is a partial fix. It de-allocated the array members
of the dynamically allocated cg_converted_list[], but fails to free()
the cg_converted_list.  Fix the resource leak by de-allocating it.

Fixes: 66799b867c7 (tools/cgxget: fix the resource leak in convert_group)
Signed-off-by: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Signed-off-by: Tom Hromatka <tom.hromatka@oracle.com>