ceph: define ceph_auth_handshake type

The definitions for the ceph_mds_session and ceph_osd both contain
five fields related only to "authorizers."  Encapsulate those fields
into their own struct type, allowing for better isolation in some
upcoming patches.

Fix the #includes in "linux/ceph/osd_client.h" to lay out their more
complete canonical path.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>

include/linux/ceph/auth.h

@@ -14,6 +14,14 @@
 struct ceph_auth_client;
 struct ceph_authorizer;
 
+struct ceph_auth_handshake {
+	struct ceph_authorizer *authorizer;
+	void *authorizer_buf;
+	size_t authorizer_buf_len;
+	void *authorizer_reply_buf;
+	size_t authorizer_reply_buf_len;
+};
+
 struct ceph_auth_client_ops {
 	const char *name;