Vet/race fixes (#4421)

This addresses all found vet/race fixes in community edition.

---------

Co-authored-by: Damian Debkowski <damian.debkowski@hashicorp.com>

internal/plugin/loopback/testing_grpc_stream_test.go

@@ -415,7 +415,7 @@ func Test_GetObjectStream(t *testing.T) {
 		}, time.Second*10, time.Millisecond*50)
 
 		require.Eventually(func() bool {
-			return stream.streamClosed && stream.IsStreamClosed()
+			return stream.IsStreamClosed()
 		}, time.Second*10, time.Millisecond*50)
 	})
 }