In virSystemdActivationClaimFDs, the memory of ent->fds has been stolen
and stored in fds, but fds is never freed, which causes a memory leak.
Fix it by declaring fds as g_autofree.
Reported-by: Jie Tang <tangjie18@huawei.com> Signed-off-by: Peng Liang <liangpeng10@huawei.com> Reviewed-by: Michal Privoznik <mprivozn@redhat.com>