Windows: Don't attempt detach VHD for R/O layers
Windows: Don't attempt detach VHD for R/O layers

Signed-off-by: John Howard <50ae662f5fcde39b7d1ed786133b7c61a25411dd@microsoft.com>

bearstech/moby,crosbymichael/docker,flavio/docker,rremer/moby,jvanz/docker,SvenDowideit/docker,trebonian/docker,gnailuy/docker,paralin/docker,docker/docker,dims/docker,gnailuy/docker,justincormack/docker,flavio/docker,yongtang/docker,thaJeztah/docker,moby/moby,jameszhan/docker,unclejack/docker,cpuguy83/docker,Mokolea/docker,SvenDowideit/docker,yosifkit/docker,ibuildthecloud/docker,kojiromike/docker,Mokolea/docker,nalind/docker,estesp/docker,Ramzec/docker,mahak/docker,unclejack/docker,paralin/docker,gnailuy/docker,moby/moby,nawawi/docker,konstruktoid/docker-upstream,nalind/docker,bearstech/moby,moby/moby,mahak/docker,moby/moby,yongtang/docker,jvanz/docker,cpuguy83/docker,pradipd/moby,Ramzec/docker,Ramzec/docker,konstruktoid/docker-1,crosbymichael/docker,jimjag/docker,vdemeester/docker,kojiromike/docker,djs55/docker,bearstech/moby,tmp6154/docker,konstruktoid/docker-upstream,bearstech/moby,docker/docker,paralin/docker,kolyshkin/moby,vdemeester/docker,moul/docker,konstruktoid/docker-1,thaJeztah/docker,jthelin/docker,yosifkit/docker,kolyshkin/moby,rremer/moby,moul/docker,trebonian/docker,cpuguy83/docker,AkihiroSuda/docker,Mokolea/docker,kolyshkin/moby,AkihiroSuda/docker,vdemeester/docker,unclejack/docker,nalind/docker,kojiromike/docker,trebonian/docker,docker/docker,yosifkit/docker,nalind/docker,crosbymichael/docker,nawawi/docker,cpuguy83/docker,jameszhan/docker,dims/docker,justincormack/docker,konstruktoid/docker-upstream,gnailuy/docker,estesp/docker,yosifkit/docker,nawawi/docker,djs55/docker,jameszhan/docker,AkihiroSuda/docker,tmp6154/docker,dims/docker,flavio/docker,pradipd/moby,ibuildthecloud/docker,mahak/docker,trebonian/docker,jvanz/docker,mahak/docker,jthelin/docker,ibuildthecloud/docker,moul/docker,ibuildthecloud/docker,pradipd/moby,Mokolea/docker,Ramzec/docker,paralin/docker,SvenDowideit/docker,nawawi/docker,jimjag/docker,justincormack/docker,moul/docker,ibuildthecloud/docker,jimjag/docker,thaJeztah/docker,konstruktoid/docker-upstream,jimjag/docker,yongtang/docker,thaJeztah/docker,konstruktoid/docker-1,djs55/docker,estesp/docker,tmp6154/docker,rremer/moby,AkihiroSuda/docker,flavio/docker