Upgrade to Go 1.9

Problem to Solve

We need to upgrade to Go 1.9 or newer to support modern API integrations such as for Vault. This also is getting more pressing as our old version of minio-go no longer works because a dependency was deleted. Users are also ending up not being able to set up a development environment with Go 1.8.7 since some development libraries do not support 1.8 anymore !1202 (comment 141849408); current work around is for deveopers to install new versions of Go.

Proposal

There are several issues that potentially impact the upgrade that need to be resolved:

• As reported in #3183 (closed) upgrading to go 1.9 or 1.10 will break automated CA Chain extraction on linux. Analysis in #4019 (closed).
• We have hit another issue where we cannot update our base image that is used for CI - more info in #3946 (closed)

Once these are out of the way, we need to do the upgrade.

When the upgrade is finished we need to pay off some technical debt with all the issues marked as upgrade GO from 1.8. Please also look on MR's related to this issue.