lxd: Log error on resultErrListAppend (#14514)

I noticed this `err` parameter was unused. So I had this idea of,
instead of removing it, logging these erros, as the errors used with
that function are currently not being disclosed to the user in any way.
This way it is clear why one was not able to get info on that particular
instance when looking in the logs. If this logging is not desirable, I
will update the PR to just remove the unused parameter.

Author: tomponline

lxd/instances_get.go

@@ -25,6 +25,7 @@ import (
 	"github.com/canonical/lxd/shared/api"
 	"github.com/canonical/lxd/shared/entity"
 	"github.com/canonical/lxd/shared/filter"
+	"github.com/canonical/lxd/shared/logger"
 	"github.com/canonical/lxd/shared/version"
 )
 
@@ -304,6 +305,8 @@ func instancesGet(d *Daemon, r *http.Request) response.Response {
 	}
 
 	resultErrListAppend := func(inst db.Instance, err error) {
+		logger.Error("Failed getting instance info", logger.Ctx{"err": err, "project": inst.Project, "instance": inst.Name})
+
 		instFull := &api.InstanceFull{
 			Instance: api.Instance{
 				Name:       inst.Name,