tcmu: Add Type of reconfig into netlink

This patch adds more info about the attribute being changed,
so that usersapce can easily figure out what is happening.

Signed-off-by: Bryant G. Ly <bryantly@linux.vnet.ibm.com>
Reviewed-By: Mike Christie <mchristi@redhat.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>