treewide: replace error comparisons and assertions with errors.Is

Change-Id: Id2424eb155f2c6842c72c5fafd124d428ef901f2
Reviewed-on: https://review.monogon.dev/c/monogon/+/2994
Tested-by: Jenkins CI
Reviewed-by: Serge Bazanski <serge@monogon.tech>
diff --git a/metropolis/node/kubernetes/csi.go b/metropolis/node/kubernetes/csi.go
index f150a13..c0d81bb 100644
--- a/metropolis/node/kubernetes/csi.go
+++ b/metropolis/node/kubernetes/csi.go
@@ -18,6 +18,7 @@
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"net"
 	"os"
@@ -107,7 +108,7 @@
 	case *csi.VolumeCapability_Mount:
 		err := unix.Mount(volumePath, req.TargetPath, "", unix.MS_BIND, "")
 		switch {
-		case err == unix.ENOENT:
+		case errors.Is(err, unix.ENOENT):
 			return nil, status.Error(codes.NotFound, "volume not found")
 		case err != nil:
 			return nil, status.Errorf(codes.Unavailable, "failed to bind-mount volume: %v", err)
diff --git a/metropolis/node/kubernetes/plugins/kvmdevice/kvmdevice.go b/metropolis/node/kubernetes/plugins/kvmdevice/kvmdevice.go
index b9b4fb4..902803b 100644
--- a/metropolis/node/kubernetes/plugins/kvmdevice/kvmdevice.go
+++ b/metropolis/node/kubernetes/plugins/kvmdevice/kvmdevice.go
@@ -26,6 +26,7 @@
 import (
 	"bytes"
 	"context"
+	"errors"
 	"fmt"
 	"net"
 	"os"
@@ -158,7 +159,7 @@
 	kvmDevNode, err := deviceNumberFromString(string(kvmDevRaw))
 
 	err = unix.Mknod("/dev/kvm", 0660, int(kvmDevNode))
-	if err != nil && err != unix.EEXIST {
+	if err != nil && errors.Is(err, unix.EEXIST) {
 		return fmt.Errorf("failed to create KVM device node: %v", err)
 	}