tstest: do not error if the there are fewer goroutines than at start
This fixes test failures like:
```
resource.go:34: goroutine count: expected 3, got 2
```
@@ -30,6 +30,9 @@ func ResourceCheck(tb testing.TB) {
time.Sleep(5 * time.Millisecond)
}
endN, endStacks := goroutines()
+ if endN <= startN {
+ return
+ }
tb.Logf("goroutine diff:\n%v\n", cmp.Diff(startStacks, endStacks))
tb.Fatalf("goroutine count: expected %d, got %d\n", startN, endN)
})
