Flaky test TestServerElasticsearchOutput

[lahsivjar]

=== RUN   TestServerElasticsearchOutput
    server_test.go:523: 
        	Error Trace:	D:/a/apm-server/apm-server/internal/beater/server_test.go:523
        	Error:      	Not equal: 
        	            	expected: map[string]interface {}{"elasticsearch":map[string]interface {}{"bulk_requests":map[string]interface {}{"available":9, "completed":0}, "indexers":map[string]interface {}{"active":1, "created":0, "destroyed":0}}}
        	            	actual  : map[string]interface {}{"elasticsearch":map[string]interface {}{"bulk_requests":map[string]interface {}{"available":8, "completed":0}, "indexers":map[string]interface {}{"active":1, "created":0, "destroyed":0}}}
        	            	
        	            	Diff:
        	            	--- Expected
        	            	+++ Actual
        	            	@@ -3,3 +3,3 @@
        	            	   (string) (len=13) "bulk_requests": (map[string]interface {}) (len=2) {
        	            	-   (string) (len=9) "available": (int64) 9,
        	            	+   (string) (len=9) "available": (int64) 8,
        	            	    (string) (len=9) "completed": (int64) 0
        	Test:       	TestServerElasticsearchOutput