build: move e2e dependencies into e2e/go.mod

Several packages are only used while running the e2e suite. These
packages are less important to update, as the they can not influence the
final executable that is part of the Ceph-CSI container-image.

By moving these dependencies out of the main Ceph-CSI go.mod, it is
easier to identify if a reported CVE affects Ceph-CSI, or only the
testing (like most of the Kubernetes CVEs).

Signed-off-by: Niels de Vos <ndevos@ibm.com>

e2e/vendor/github.com/mistifyio/go-zfs/error.go

@@ -0,0 +1,18 @@
+package zfs
+
+import (
+	"fmt"
+)
+
+// Error is an error which is returned when the `zfs` or `zpool` shell
+// commands return with a non-zero exit code.
+type Error struct {
+	Err    error
+	Debug  string
+	Stderr string
+}
+
+// Error returns the string representation of an Error.
+func (e Error) Error() string {
+	return fmt.Sprintf("%s: %q => %s", e.Err, e.Debug, e.Stderr)
+}