Issue/272 change apmserver check from okHttp to URLConnection

[ghost]

closes #272

[elasticmachine]

Since this is a community submitted pull request, a Jenkins build has not been kicked off automatically. Can an Elastic organization member please verify the contents of this patch and then kick off a build manually?

[ghost]

Hi @nugusbayevkk, we have found your signature in our records, but it seems like you have signed with a different e-mail than the one used in yout Git commit. Can you please add both of these e-mails into your Github profile (they can be hidden), so we can match your e-mails to your Github profile?

[felixbarny]

Thanks for this PR :)

Some notes:

• There is a strange JulBridgeLogger.java_406862764079074 file which should be deleted
• It's ok for the tests to use OkHttp, please revert the test changes as it's simpler to write the tests using OkHttp :)

[felixbarny]

Also remove the okhttp and okio relocation patterns in elastic-apm-agent/pom.xml

[felixbarny]

Just a minor thing, probably a leftover from testing. Other than that, LGTM :)

[felixbarny]

Jenkins test this please