bump min required docker version for build
bump min required docker version for build

to the same version we use everywhere else, e.g. in weaveexec

philipz/weave,rade/weave,philipz/weave,narry/weave,awh/weave,ycaihua/weave,ycaihua/weave,awh/weave,cgvarela/weave,n054/weave,rade/weave,n054/weave,awh/weave,rade/weave,weaveworks/weave,squaremo/weave,dpw/weave,narry/weave,paladin74/weave,OnePaaS/weave,paladin74/weave,philipz/weave,OnePaaS/weave,2opremio/weave,achanda/weave,narry/weave,ycaihua/weave,squaremo/weave,weaveworks/weave,weaveworks/weave,achanda/weave,cgvarela/weave,errordeveloper/weave,kidaa/weave,kidaa/weave,dpw/weave,paulbellamy/weave,n054/weave,bboreham/weave,achanda/weave,philipz/weave,rade/weave,kidaa/weave,tomwilkie/weave,awanke/weave,rade/weave,OnePaaS/weave,aaam/weave,paulbellamy/weave,aaam/weave,awh/weave,beni55/weave,paulbellamy/weave,errordeveloper/weave,philipz/weave,awanke/weave,n054/weave,BWITS/weave,awh/weave,dpw/weave,2opremio/weave,weaveworks/weave,n054/weave,tomwilkie/weave,paulbellamy/weave,paladin74/weave,cgvarela/weave,bboreham/weave,BWITS/weave,achanda/weave,ycaihua/weave,paladin74/weave,errordeveloper/weave,awanke/weave,dpw/weave,squaremo/weave,bboreham/weave,awanke/weave,BWITS/weave,OnePaaS/weave,BWITS/weave,cgvarela/weave,cgvarela/weave,bboreham/weave,tomwilkie/weave,dpw/weave,kidaa/weave,2opremio/weave,beni55/weave,tomwilkie/weave,errordeveloper/weave,aaam/weave,narry/weave,beni55/weave,aaam/weave,squaremo/weave,2opremio/weave,ycaihua/weave,kidaa/weave,errordeveloper/weave,achanda/weave,OnePaaS/weave,narry/weave,2opremio/weave,bboreham/weave,squaremo/weave,beni55/weave,BWITS/weave,paladin74/weave,aaam/weave,tomwilkie/weave,awanke/weave,beni55/weave