ctl: add more apis

[zhyass]

Path:    /v1/cluster/add
Method:  POST
Request: {
    "address": "The endpoint address of this peer",  [required]
}

Path:    /v1/cluster/remove
Method:  POST
Request: {
    "address": "The endpoint address of this peer",  [required]
}

Path:    /v1/raft/trytoleader
Method:  POST

Path:    /v1/xenon/ping
Method:  GET

[codecov[bot]]

Codecov Report

Merging #145 (6a4951a) into feature_adapt_k8s (fa77d8d) will increase coverage by 1%. The diff coverage is 73%.

@@                Coverage Diff                @@
##           feature_adapt_k8s   #145    +/-   ##
=================================================
+ Coverage                 67%    69%    +1%     
=================================================
  Files                     48     51     +3     
  Lines                   3731   4565   +834     
=================================================
+ Hits                    2528   3150   +622     
- Misses                   966   1165   +199     
- Partials                 237    250    +13     

Impacted Files	Coverage Δ
src/mysql/api.go	66% <0%> (+5%)	:arrow_up:
src/raft/attr.go	91% <ø> (+1%)	:arrow_up:
src/mysql/mysqlbase.go	88% <45%> (+2%)	:arrow_up:
src/ctl/v1/xenon.go	53% <53%> (ø)
src/mysql/mysql56.go	84% <63%> (+13%)	:arrow_up:
src/ctl/v1/cluster.go	65% <65%> (ø)
src/ctl/v1/raft.go	66% <66%> (ø)
src/raft/leader.go	86% <80%> (-1%)	:arrow_down:
src/server/server.go	56% <83%> (+5%)	:arrow_up:
src/xbase/xrpc/xrpc.go	85% <84%> (+2%)	:arrow_up:
... and 55 more

---

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[andyli029]

Good job.