Update to elastic/beats@27e76c567711 (#5382)

* Update to elastic/beats@27e76c567711

- Update to Go 1.16.4
- Adapt to elastic/beats#25696

* golint fixes

* tests: chown go.sum files

go mod download will download all modules, even
if they are not used (e.g. dependencies of parts
of beats that are not dependencies of apm-server).
As such the command may need to update go.sum,
so make sure it is owned by the running user.

* Add gotestsum to go.mod

version.asciidoc

@@ -1,6 +1,6 @@
 // doc-branch can be: master, 8.0, 8.1, etc.
 :doc-branch: master
-:go-version: 1.15.12
+:go-version: 1.16.4
 :python: 3.7
 :docker: 1.12
 :docker-compose: 1.11