Description of problem:
Prepare ocp with etcd2 installed, after swap etcd2 to etcd3, services restart failed.

Version-Release number of selected component (if applicable):
etcd-2.3.7-4.el7.x86_64
etcd3-3.0.3-1.el7.x86_64

How reproducible:
sometimes

Steps to Reproduce:
1. prepare a env with etcd2
2. [root@etcd ~]# yum swap etcd etcd3 -y
3. [root@etcd ~]# systemctl restart etcd

Actual results:
etcd service restart failed

[root@etcd ~]# journalctl -xe -u etcd
...
Jan 06 08:18:00 etcd.example.com etcd[124364]: database file (/var/lib/etcd/member/snap/db index 0) does not match with snapshot (index 1150115).
Jan 06 08:18:00 etcd.example.com systemd[1]: etcd.service: main process exited, code=exited, status=1/FAILURE
Jan 06 08:18:00 etcd.example.com systemd[1]: Failed to start Etcd Server.
...

Expected results:
etcd service restart success

Additional info: