Support service version for the Go Profiler
This includes a small refactor in order allow passing arguments to the profiler initializer (initProfiler).
It's required once the environment that our Go
services run does not include some data at
environment variables such as GAE_VERSION(which only happen to
exist at Google App Engine).
So given this information is already given to the Serve function (via Go services that use it), we take advantage of that for
passing it over to the profiler.
As an outcome, this service version will be presented at a list in Version on Stackdriver Profiler UI.
For more details about the library we use for Stackdriver: https://godoc.org/cloud.google.com/go/profiler
Edited by Oswaldo Ferreira