* Install missing plugins on startup
This commit addresses the problem of missing plugins by scanning the
snapshot and language host on startup for the list of required plugins
and, if there are any plugins that are required but not installed,
installs them. The mechanism by which plugins are installed is exactly
the same as 'pulumi plugin install'.
The installation of missing plugins is best-effort and, if it fails,
will not fail the update.
This commit addresses pulumi/pulumi-azure#200, where users using Pulumi
in CI often found themselves missing plugins.
* Add CHANGELOG
* Skip downloading plugins if no client provided
* Reduce excessive test output
* Update Gopkg.lock
* Update pkg/engine/destroy.go
Co-Authored-By: swgillespie <sean@pulumi.com>
* CR: make pluginSet a newtype
* CR: Assign loop induction var to local var