clientv3/integration: add member promote failure test cases

[jingyih]

Add 2 failure cases for member promote. "Learner not ready" failure case is already covered in TestMemberPromote[1]. This PR completes all 3 cases mentioned in the doc [2].

cc @xiang90 @WIZARD-CXY @gyuho

Reference:
[1]

etcd/clientv3/integration/cluster_test.go

Lines 253 to 255 in 2f7121b

	// learner is not started yet. Expect learner progress check to fail.
	// As the result, member promote request will fail.
	_, err = capi.MemberPromote(context.Background(), learnerID)

[2] Doc: Error cases when promoting a learner member

[codecov-io]

Codecov Report

Merging #10775 into master will increase coverage by 0.2%.
The diff coverage is n/a.

@@            Coverage Diff            @@
##           master   #10775     +/-   ##
=========================================
+ Coverage   62.51%   62.72%   +0.2%     
=========================================
  Files         392      392             
  Lines       37157    37157             
=========================================
+ Hits        23230    23305     +75     
+ Misses      12330    12280     -50     
+ Partials     1597     1572     -25

Impacted Files	Coverage Δ
client/client.go	48.03% <0%> (-25.5%)	⬇️
auth/jwt.go	44.76% <0%> (-23.81%)	⬇️
client/members.go	65.32% <0%> (-20.17%)	⬇️
auth/store.go	55.09% <0%> (-10.97%)	⬇️
pkg/adt/interval_tree.go	78.07% <0%> (-5.71%)	⬇️
clientv3/leasing/txn.go	88.09% <0%> (-3.18%)	⬇️
proxy/grpcproxy/watch.go	88.55% <0%> (-3.02%)	⬇️
proxy/httpproxy/director.go	77.14% <0%> (-2.86%)	⬇️
etcdserver/api/rafthttp/msgappv2_codec.go	69.56% <0%> (-1.74%)	⬇️
lease/leasehttp/http.go	62.77% <0%> (-1.46%)	⬇️
... and 29 more

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[xiang90]

move to line 23

[jingyih]

Thanks. Fixed.

[xiang90]

lgtm

[WIZARD-CXY]

lgtm