Add Travis-CI build for RBD Docker Plug-in
Add Travis-CI build for RBD Docker Plug-in

This patch updates the .travis.yml file to add a build for the RBD
Docker plug-in.

oppodeldoc/rexray,thecodeteam/rexray,cduchesne/rexray,emccode/rexray,oppodeldoc/rexray,akutz/rexray,cduchesne/rexray,oppodeldoc/rexray,emccode/rexray,codedellemc/rexray,codedellemc/rexray,akutz/rexray,akutz/rexray,oppodeldoc/rexray,codedellemc/rexray,codedellemc/rexray,thecodeteam/rexray,emccode/rexray,cduchesne/rexray,akutz/rexray,oppodeldoc/rexray,thecodeteam/rexray,thecodeteam/rexray,cduchesne/rexray,akutz/rexray,oppodeldoc/rexray,cduchesne/rexray,thecodeteam/rexray,codedellemc/rexray,cduchesne/rexray,thecodeteam/rexray,codedellemc/rexray,emccode/rexray,akutz/rexray