Added capability to send metrics through Http API for OpenTSDB

[EricFortin]

Modified the opentsdb output plugin so it can also use Http API to send metrics. The Http API has better error management and is easier to debug. Should I squash my changes ? First time contributing.

Required for all PRs:

• CHANGELOG.md updated
• Sign CLA (if not already signed)

[sparrc]

remove "Telnet Mode"

[sparrc]

rather than having a use_http option, I would prefer if you integrated it with the name of the host, and then parse out the "scheme" from the url.

ie,

host = "opentsdb.example.com" <-- use tcp
host = "tcp://opentsdb.example.com" <-- use tcp
host = "http://opentsdb.example.com" <-- use http

[EricFortin]

I will implement the selection of API based on the host and update the PR. Should I go ahead and update Changelog ?

[sparrc]

yes, please do, also don't worry about squashing, I can do that within github

[EricFortin]

All done I think. Let me know if anythings is missing. Also, do this have a chance of getting in 1.0 ?

[EricFortin]

@sparrc Anything else you need from me ?

[EricFortin]

@sparrc I had a look at the test failure but I don't see how I my code could affect this. I also checked PR #1543 which had the same problem with totally unrelated code I think. I then ran the test locally and the tail tests passed just fine. What would be the next step ?

[sparrc]

sorry for the noise, I will kick a rebuild.

I don't think there is anything else, I just need to find time to review again and merge, there is a lot on my plate at the moment so please be patient.

[EricFortin]

@sparrc No problem and thanks !

[sparrc]

why did you make this type? just using a map[string]string is more explicit and readable throughout

[EricFortin]

@sparrc I did what you suggested.

[sparrc]

Thanks @EricFortin, but it looks like your CHANGELOG rebase might have gotten mixed up with other commits. Can you please revert your CHANGELOG change and then rebase, putting your PR into the 1.1 release?

[EricFortin]

@sparrc Should be good now. Thanks.