Set backend to cindex before recovering the lessor in applySnapshot

[ahrtr]

Fix 13922.

Copy the comment I added in the source code here so as save the effort to explain again:

	// We need to set the backend to consistIndex before recovering the lessor,
	// because lessor.Recover will commit the boltDB transaction, accordingly it
	// will get the old consistent_index persisted into the db in OnPreCommitUnsafe.
	// Eventually the new consistent_index value coming from snapshot is overwritten
	// by the old value.

[codecov-commenter]

Codecov Report

Merging #13930 (484d2f0) into main (dd08e15) will increase coverage by 0.06%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main   #13930      +/-   ##
==========================================
+ Coverage   72.51%   72.57%   +0.06%     
==========================================
  Files         469      469              
  Lines       38411    38411              
==========================================
+ Hits        27853    27878      +25     
+ Misses       8778     8755      -23     
+ Partials     1780     1778       -2     

Flag	Coverage Δ
all	72.57% <100.00%> (+0.06%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
server/etcdserver/server.go	84.54% <100.00%> (ø)
raft/rafttest/node.go	95.00% <0.00%> (-5.00%)	⬇️
server/etcdserver/api/v3rpc/watch.go	83.55% <0.00%> (-3.03%)	⬇️
client/pkg/v3/transport/listener.go	57.18% <0.00%> (-2.40%)	⬇️
server/auth/store.go	85.76% <0.00%> (-0.34%)	⬇️
server/etcdserver/v3_server.go	78.17% <0.00%> (+0.17%)	⬆️
raft/raft.go	90.42% <0.00%> (+0.24%)	⬆️
client/v3/leasing/kv.go	90.69% <0.00%> (+0.33%)	⬆️
pkg/proxy/server.go	61.01% <0.00%> (+0.33%)	⬆️
client/v3/watch.go	93.37% <0.00%> (+0.40%)	⬆️
... and 11 more

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[ahrtr]

cc @ptabor @serathius @spzala

[ahrtr]

Will backport to 3.5, once it's merged.

[ptabor]

Awesome catch !!!

[serathius]

Confirmed that this addresses the issue, awesome work!