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/internal/errutil/strerror.go

@@ -0,0 +1,45 @@
+/*
+Package errutil provides common functions for dealing with error conditions for
+all ceph api wrappers.
+*/
+package errutil
+
+/* force XSI-complaint strerror_r() */
+
+// #define _POSIX_C_SOURCE 200112L
+// #undef _GNU_SOURCE
+// #include <stdlib.h>
+// #include <errno.h>
+// #include <string.h>
+import "C"
+
+import (
+	"unsafe"
+)
+
+// FormatErrno returns the absolute value of the errno as well as a string
+// describing the errno. The string will be empty is the errno is not known.
+func FormatErrno(errno int) (int, string) {
+	buf := make([]byte, 1024)
+	// strerror expects errno >= 0
+	if errno < 0 {
+		errno = -errno
+	}
+
+	ret := C.strerror_r(
+		C.int(errno),
+		(*C.char)(unsafe.Pointer(&buf[0])),
+		C.size_t(len(buf)))
+	if ret != 0 {
+		return errno, ""
+	}
+
+	return errno, C.GoString((*C.char)(unsafe.Pointer(&buf[0])))
+}
+
+// StrError returns a string describing the errno. The string will be empty if
+// the errno is not known.
+func StrError(errno int) string {
+	_, s := FormatErrno(errno)
+	return s
+}