Replace the default Logger in some examples with a locally constructed
Logger.
Calling SetDefault changes global state that could affect other tests.
Although we could use a defer to restore the state, that clutters
the example and would not work if tests were run concurrently.
Change-Id: Ib2595c57f8e6c3e0b39b982f682ba287c2ae249d
Reviewed-on: https://go-review.googlesource.com/c/go/+/482475
Run-TryBot: Jonathan Amsterdam <jba@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Alan Donovan <adonovan@google.com>