Increase default etcdraft tick interval to 500ms, for several reasons:
- in a WAN/Cloud environment, this is more realistic
- WAL sync in CI often exceeds 1s, which causes heartbeats not being
  sent timely. Increasing election timeout can decrease the chance of
  unexpected leader failover.

This CR also increases default timeout of peer cmd, because now
it takes 5~10s to elect a leader for a newly created channel, and
`peer channel create` can only retrieve genesis block of that channel
when leader exists (Deliver API returns error if leaderless).

Note that this value is still configurable by users.

Change-Id: I94fbbc750fa096cce6ef9e2d65eb981c6202b675
Signed-off-by: Jay Guo <guojiannan1101@gmail.com>