pkg/kvstore: fix nil pointer in error while doing a transaction in etcd
pkg/kvstore: fix nil pointer in error while doing a transaction in etcd

txnresp can obviously be nil if err is != nil. We should check if
txnresp.Succeeded after checking if err == nil first.

Fixes: 84291c30ece5 ("pkg/kvstore: implement new *IfLocked methods for etcd")
Signed-off-by: André Martins <bc9800b9d52a24cce72a73dd528afed53f10e5fc@cilium.io>

tklauser/cilium,cilium-team/cilium,tgraf/cilium,tklauser/cilium,cilium/cilium,tgraf/cilium,tklauser/cilium,tklauser/cilium,cilium/cilium,cilium/cilium,michi-covalent/cilium,tgraf/cilium,michi-covalent/cilium,tgraf/cilium,michi-covalent/cilium,cilium/cilium,tklauser/cilium,michi-covalent/cilium,tgraf/cilium,cilium/cilium,tgraf/cilium,cilium-team/cilium,michi-covalent/cilium