vzctl_*_snapshot: fix compiler warnings about param.guid

Made ploop_merge_param.guid const in ploop lib so we can skip the cast.

Unfortunately we can't make ploop_snapshot_param.guid field const
because sometimes it's filled in by ploop lib. So let's use strdup().

Signed-off-by: Kir Kolyshkin <kir@openvz.org>
1 file changed