Follow-up from #943

[mheese]

Follow-up from #943 . Adding better logging for http client certs and adding stops in envoy.

There could be a lot more done in both packages that are touched here. However, especially the http package stands out: logging is not very clear, UT missing (in the works though for envoy by Abhi), a lot of variable/pointer checks missing, unclear return values and missing errors - should at least have a comment if they are intended, ignoring golang best practices and not very elegant code. One can see that this was written down in a hurry, and fixed in a hurry by us recently as well :) This package deserves some love.

Anyway, I leave it up to @brianonn and @abhijitherekar to add more to this PR if you think that is necessary.

@brianonn I ignored the Gopkg.toml comment from #943 as I don't think we need to change anything. Please comment here if you think otherwise.

[brianonn]

Nice! thanks @mheese . I like the way you made your changes.

I still think we should pin the Gopkg.toml entry for conntrack and not let it float around with master.

[[constraint]]
  name = "github.com/ti-mo/conntrack"
  revision = "c9b176489c1a057922cbaa0a78df9e51cffbcc0d"

Is there a reason why you think this is not necessary? I never like choosing a branch tip and I always like to have it pinned to a commit and reproducible, rather than allow the version we pull in to change (and possibly open it to new bugs or security holes that are introduced)