server: fix testings

Make WaitMode panic to alert.
etcd: make retry configurable
Merge pull request #30 from etcd-team/etcd_config_retry

etcd: make retry configurable
store: fix the bug caused by random iteration order over map
Merge pull request #42 from etcd-team/fix-store

store: fix the bug caused by random iteration order over map
etcd: attach default scheme to the peer-list if scheme is not given