Update etcd.go

etcdmain: Fix misuse "-addr" flag

In code, it uses "-advertise-client-urls" or "-addr" flags to get the list of this member's peer URLs, 
It should be using "-peer-addr" flag instead of "-addr" flag.
build: statically compile etcdctl binary
etcdserver: improve discovery ignore warning
rafthttp: improve start/stop logging
rafthttp: feedback
Merge pull request #1898 from robszumski/improve-logging

Improve logging for etcdserver and rafthttp
migrate: improve logging for name and ID
rafthttp: log the type of message that is dropped when sending
Merge pull request #1906 from yichengq/261

rafthttp: log the type of message that is dropped when sending
raft: get rid of allocation
docs: make clear that dashboard is a module
raft: remove panic when we see a proposal with no leader.

This panic can never be reached when using raft.Node, because we only
read from propc when there is a leader. However, it is possible to see
this error when using raft the raft object directly (as in MultiNode),
and in this case it is better to simply drop the proposal (as if we had
sent it to a leader that immediately vanished).

Add an error return to MemoryStorage.Append for consistency.
Merge pull request #1907 from robszumski/dash-note

docs: make clear that dashboard is a module
raft: support to do multiple proposals in one message
rafthttp: batch MsgProp

If amounts of MsgProp goes to the follower, it could batch them and
forward to the leader. This can avoid dropping MsgProp in good path
due to exceed maximal serving in sender.

Moreover, batching MsgProp can increase the throughput of proposals that
come from follower.
Merge pull request #1901 from yichengq/260

rafthttp: batch MsgProp
Merge pull request #1897 from xiang90/raft

raft: get rid of the using of defer in critical path
rafthttp: fixes issue 1903

Record the URL being fetched in the log when we 404
Merge pull request #1911 from diffoperator/issue_1903

rafthttp: fixes issue 1903
discovery: discovery will try forever when there is a timeout.

Perviously, etcd retries three times for timeout error. After this
commit, etcd retries forever. Also this commit make etcd client
aware of gateway timetout.