net/http: make use of maps.Clone for Transport.{Clone, RegisterProtocol}
Not a big deal, maybe it's a bit clearer that it's cloning a map.
Change-Id: I7c85382a01df97d1f58109b2483061e6decdf03a
GitHub-Last-Rev:
7a88af7f56ab7ad017081187e226e901752fa8bc
GitHub-Pull-Request: golang/go#69357
Reviewed-on: https://go-review.googlesource.com/c/go/+/612015
Auto-Submit: Damien Neil <dneil@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Damien Neil <dneil@google.com>