Merge pull request #1560 from dongluochen/update_swarm_v1.2.0-rc1

update swarm v1.2.0-rc1

library/swarm

@@ -10,4 +10,5 @@
 1.1.1: git://github.com/docker/swarm-library-image@9346bd71c2a9b1433a663b8c2fe20b2636585f54
 1.1.2: git://github.com/docker/swarm-library-image@5f284e33ef90b7bc30684ad09a5261c037fc9d5e
 1.1.3: git://github.com/docker/swarm-library-image@4d298d3113a4ecefa83a3f9e18f4aaf4f95f007e
+1.2.0-rc1: git://github.com/docker/swarm-library-image@703192c7907b3d30e20d68a8353b25110a2a290c
 latest: git://github.com/docker/swarm-library-image@4d298d3113a4ecefa83a3f9e18f4aaf4f95f007e