feature:Use rpc to get file information from other supernodes(HA second part)

[yunfeiyanggzq]

Signed-off-by: yunfeiyangbuaa [email protected]

Ⅰ. Describe what this PR did

this pr is a branch of #694 and should be merged after #694 and #682
this pr is the second part of supernode ha.in first part,I use etcd to implement active/standby switch.In this pr, I add a cli command to use supernode ha,and add two function in ha_magr,one make active supernode sensing standby supernode's status.Another one send dfget's request copy to standby supernode.

Ⅱ. Does this pull request fix one issue?

Ⅲ. Why don't you add test cases (unit test/integration test)? (你真的觉得不需要加测试吗？)

Ⅳ. Describe how to verify it

Ⅴ. Special notes for reviews

my pr will be submitted as follows

• 1.implement a ha_mgr to implement active/standby switch-----done
• 2.add a cmd config to config ha ,use ha_mgr to change supernode status between active and standby ----done
• 3.add new interface to ha_mgr(active supernode send a copy of all the dfget's request to standby supernode to implement state synchronization )
• 4.modify dfget's code(dfget can go on it's work after the active supernode is off)
• 5.implement the vip

[codecov-io]

Codecov Report

Merging #741 into master will decrease coverage by 1.06%.
The diff coverage is 6.07%.

@@            Coverage Diff             @@
##           master     #741      +/-   ##
==========================================
- Coverage   39.66%   38.59%   -1.07%     
==========================================
  Files         109      109              
  Lines        6429     6627     +198     
==========================================
+ Hits         2550     2558       +8     
- Misses       3671     3855     +184     
- Partials      208      214       +6

Impacted Files	Coverage Δ
supernode/server/0.3_bridge.go	0% <0%> (ø)	⬆️
supernode/daemon/mgr/task/manager_util.go	17.85% <0.95%> (-6.45%)	⬇️
supernode/config/config.go	51.56% <15.78%> (-15.11%)	⬇️
supernode/daemon/mgr/peer/manager.go	77.41% <60%> (-1.24%)	⬇️
supernode/server/server.go	41.37% <60%> (+0.63%)	⬆️
supernode/daemon/mgr/task/manager.go	24.22% <7.89%> (-5.94%)	⬇️
hack/boilerplate/check-boilerplate.go	33.33% <0%> (-3.26%)	⬇️
supernode/daemon/mgr/progress/progress_delete.go	0% <0%> (ø)	⬆️
dfget/config/config.go	91.76% <0%> (ø)	⬆️
...t/core/downloader/p2p_downloader/p2p_downloader.go	0% <0%> (ø)	⬆️

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[pouchrobot]

ping @yunfeiyanggzq
Conflict happens after merging a previous commit.
Please rebase the branch against master and push it back again. Thanks a lot.