rebase: use go-ceph v0.3.0

v0.3.0 adds support for rbd.FeatureSet that can be used to parse the
features of an RBD image. This will be used in the followup commit that
adds rbdVolume.getImageInfo().

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

vendor/github.com/ceph/go-ceph/rbd/watchers_mimic.go

@@ -0,0 +1,57 @@
+// +build !luminous
+//
+// Ceph Mimic is the first version that supports watchers through librbd.
+
+package rbd
+
+// #cgo LDFLAGS: -lrbd
+// #include <errno.h>
+// #include <rbd/librbd.h>
+import "C"
+
+// ImageWatcher is a representation of the rbd_image_watcher_t from librbd.h
+type ImageWatcher struct {
+	Addr   string
+	Id     int64
+	Cookie uint64
+}
+
+// ListWatchers returns the watchers on an RBD image. In case of an error, nil
+// and an error are returned.
+//
+// Note:
+//   Only supported in Ceph Mimic and newer.
+//
+// Implements:
+//   int rbd_watchers_list(rbd_image_t image,
+//                         rbd_image_watcher_t *watchers, size_t *max_watchers)
+func (image *Image) ListWatchers() ([]ImageWatcher, error) {
+	if err := image.validate(imageIsOpen); err != nil {
+		return nil, err
+	}
+
+	count := C.ulong(0)
+	ret := C.rbd_watchers_list(image.image, nil, &count)
+	if ret != 0 && ret != -C.ERANGE {
+		return nil, getError(ret)
+	}
+	if ret == 0 && count == 0 {
+		return nil, nil
+	}
+
+	watchers := make([]C.rbd_image_watcher_t, count)
+	ret = C.rbd_watchers_list(image.image, &watchers[0], &count)
+	if ret != 0 && ret != -C.ERANGE {
+		return nil, getError(ret)
+	}
+	defer C.rbd_watchers_list_cleanup(&watchers[0], count)
+
+	imageWatchers := make([]ImageWatcher, len(watchers))
+	for i, watcher := range watchers {
+		imageWatchers[i].Addr = C.GoString(watcher.addr)
+		imageWatchers[i].Id = int64(watcher.id)
+		imageWatchers[i].Cookie = uint64(watcher.cookie)
+	}
+
+	return imageWatchers, nil
+}