Noticed during my audit, the code for cache.CommitKVStoreCacheManager.Reset()
discarded the prior on every invocation i.e.
m = make(map[T(key)]T(value))
However, this can be made fast and conserve memory by using the map clearing idiom
that the Go compiler recognizes i.e.
for key := range m {
delete(m, key)
}
and turns into very fast code, instead of the extraneous map discarding.
The speed up generated is:
```shell
$ benchstat before after
name old time/op new time/op delta
Reset-8 204ns ± 2% 66ns ± 9% -67.86% (p=0.000 n=20+20)
name old alloc/op new alloc/op delta
Reset-8 384B ± 0% 0B -100.00% (p=0.000 n=20+20)
name old allocs/op new allocs/op delta
Reset-8 3.00 ± 0% 0.00 -100.00% (p=0.000 n=20+20)
```
Fixes#6681
Robert Zaremba
Emmanuel T Odeke
Alexander Bezobchuk