Flaky test TestPayloadBytes

Job: https://gitlab.com/gitlab-org/gitaly/-/jobs/1789058532

=== RUN   TestPayloadBytes
    log_test.go:127: 
        	Error Trace:	log_test.go:127
        	Error:      	"[%!s(*logrus.Entry=&{0xc000253340 map[grpc.code:OK grpc.method:UnaryCall grpc.request.payload_bytes:8 grpc.response.payload_bytes:8 grpc.service:grpc.testing.TestService grpc.start_time:2021-11-16T18:01:19Z grpc.time_ms:0.078 span.kind:server system:grpc] {13861264209798868921 36528877 0x13046c0} 4 <nil> finished unary call with code OK <nil> 0xc0000a75f0 }) %!s(*logrus.Entry=&{0xc000253340 map[grpc.code:OK grpc.method:HalfDuplexCall grpc.request.payload_bytes:16 grpc.response.payload_bytes:16 grpc.service:grpc.testing.TestService grpc.start_time:2021-11-16T18:01:19Z grpc.time_ms:0.287 span.kind:server system:grpc] {13861264209802457861 40117827 0x13046c0} 4 <nil> finished streaming call with code OK <nil> 0xc0003dcd50 }) %!s(*logrus.Entry=&{0xc000253340 map[grpc.code:OK grpc.method:HalfDuplexCall grpc.request.payload_bytes:16 grpc.response.payload_bytes:16 grpc.service:grpc.testing.TestService grpc.start_time:2021-11-16T18:01:19Z grpc.time_ms:0.21 span.kind:server system:grpc] {13861264209806744740 44404706 0x13046c0} 4 <nil> finished streaming call with code OK <nil> 0xc0003ec270 })]" should have 4 item(s), but has 3
        	Test:       	TestPayloadBytes
--- FAIL: TestPayloadBytes (0.02s)

/cc @8bitlife