Add support for changed rados_write API.

Seems from version 0.68 to 0.69 the rados_write
function all of a sudden gives back 0 when succeeded and
no longer the actual bytes it wrote. As we also want to
support the old API it now checks the LIBRADOS_VERSION_CODE

src/stored/backends/rados_device.c

@@ -268,34 +268,58 @@ ssize_t rados_device::d_read(int fd, void *buffer, size_t count)
 
 /*
  * Write data to a volume using librados.
+ *
+ * Seems the API changed everything earlier then 0.69 returns bytes written.
  */
+#if LIBRADOS_VERSION_CODE <= 17408
 ssize_t rados_device::d_write(int fd, const void *buffer, size_t count)
 {
    if (m_ctx) {
       int nr_written;
 
+      nr_written = rados_write(m_ctx, getVolCatName(), (char *)buffer, count, m_offset);
+
+      if (nr_written >= 0) {
+         m_offset += nr_written;
+         return nr_written;
+      } else {
+         errno = -nr_written;
+         return -1;
+      }
+   } else {
+      errno = EBADF;
+      return -1;
+   }
+}
+#else
+ssize_t rados_device::d_write(int fd, const void *buffer, size_t count)
+{
+   if (m_ctx) {
+      int status;
+
 #ifdef HAVE_RADOS_STRIPER
       if (m_striper) {
-         nr_written = rados_striper_write(m_striper, getVolCatName(), (char *)buffer, count, m_offset);
+         status = rados_striper_write(m_striper, getVolCatName(), (char *)buffer, count, m_offset);
       } else {
 #endif
-         nr_written = rados_write(m_ctx, getVolCatName(), (char *)buffer, count, m_offset);
+         status = rados_write(m_ctx, getVolCatName(), (char *)buffer, count, m_offset);
 #ifdef HAVE_RADOS_STRIPER
       }
 #endif
 
-      if (nr_written >= 0) {
-         m_offset += nr_written;
-         return nr_written;
+      if (status == 0) {
+         m_offset += count;
+         return count;
       } else {
-         errno = -nr_written;
+         errno = -status;
          return -1;
       }
    } else {
       errno = EBADF;
       return -1;
    }
 }
+#endif
 
 int rados_device::d_close(int fd)
 {