flaky-test: TestLeaderController_AddFollower

[mattisonchao]

--- FAIL: TestLeaderController_AddFollower (0.01s)
    leader_controller_test.go:567: 
        	Error Trace:	/home/runner/work/oxia/oxia/server/leader_controller_test.go:567
        	Error:      	Received unexpected error:
        	            	leaked iterators:
        	            	(1) attached stack trace
        	            	  -- stack trace:
        	            	  | github.com/cockroachdb/pebble.(*DB).Close
        	            	  | 	/home/runner/go/pkg/mod/github.com/cockroachdb/[email protected]/db.go:1632
        	            	  | github.com/oxia-db/oxia/server/kv.(*Pebble).Close
        	            	  | 	/home/runner/work/oxia/oxia/server/kv/kv_pebble.go:362
        	            	  | github.com/oxia-db/oxia/server/kv.(*db).Close
        	            	  | 	/home/runner/work/oxia/oxia/server/kv/db.go:187
        	            	  | github.com/oxia-db/oxia/server.(*leaderController).close
        	            	  | 	/home/runner/work/oxia/oxia/server/leader_controller.go:969
        	            	  | github.com/oxia-db/oxia/server.(*leaderController).Close
        	            	  | 	/home/runner/work/oxia/oxia/server/leader_controller.go:941
        	            	  | github.com/oxia-db/oxia/server.TestLeaderController_AddFollower
        	            	  | 	/home/runner/work/oxia/oxia/server/leader_controller_test.go:567
        	            	  | testing.tRunner
        	            	  | 	/opt/hostedtoolcache/go/1.24.6/x64/src/testing/testing.go:1792
        	            	  | runtime.goexit
        	            	  | 	/opt/hostedtoolcache/go/1.24.6/x64/src/runtime/asm_amd64.s:1700
        	            	Wraps: (2) leaked iterators:
        	            	  | 0.0:
        	            	  |   000004:[__oxia/term#10,SET-__oxia/term-options#11,SET]
        	            	Error types: (1) *withstack.withStack (2) *errutil.leafError
        	Test:       	TestLeaderController_AddFollower