admin_socket.cc: Use older sizeof syntax
admin_socket.cc: Use older sizeof syntax

Fix compilation for compilers that don't support the
sizeof(type::field_name) syntax.

Signed-off-by: Colin McCabe <7b35906f1d014e74a9dc8c913eb229119df647aa@dreamhost.com>

ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph