util: Port all code to new errwrap package

This should keep things more uniform.

engine/resources/aws_ec2.go

@@ -34,6 +34,7 @@ import (
 
 	"github.com/purpleidea/mgmt/engine"
 	"github.com/purpleidea/mgmt/engine/traits"
+	"github.com/purpleidea/mgmt/util/errwrap"
 
 	"github.com/aws/aws-sdk-go/aws"
 	"github.com/aws/aws-sdk-go/aws/awserr"
@@ -43,7 +44,6 @@ import (
 	"github.com/aws/aws-sdk-go/service/ec2"
 	"github.com/aws/aws-sdk-go/service/sns"
 	multierr "github.com/hashicorp/go-multierror"
-	errwrap "github.com/pkg/errors"
 )
 
 func init() {