Remove invalid docker build flag in travis build
Remove invalid docker build flag in travis build

gongbp/ping-play,brikis98/ping-play,brikis98/ping-play,jasonchaffee/ping-play,gongbp/ping-play,jasonchaffee/ping-play,gongbp/ping-play,jasonchaffee/ping-play,carlosFattor/ping-play,carlosFattor/ping-play,carlosFattor/ping-play,brikis98/ping-play,dandeeee/ping-play,dandeeee/ping-play,dandeeee/ping-play