projectquota: treat ENOSYS as quota unsupported
projectquota: treat ENOSYS as quota unsupported

If mknod() returns ENOSYS, it most probably means quota is not supported
here, so return the appropriate error.

This is a conservative* fix to regression in vfs graph driver introduced
by commit 7a1618ced359a3ac92 ("add quota support to VFS graphdriver").
On some filesystems, vfs fails to init with the following error:

> Error starting daemon: error initializing graphdriver: Failed to mknod
> /go/src/github.com/docker/docker/bundles/test-integration/d6bcf6de610e9/root/vfs/backingFsBlockDev:
> function not implemented

Reported-by: Brian Goff <dc73d0991b982a8303e713ef531a313af77e242a@gmail.com>
Signed-off-by: Kir Kolyshkin <3a017b8ddb3f9cf3e4a59978b004111bdeb97f08@gmail.com>

justincormack/docker,Mokolea/docker,nalind/docker,ibuildthecloud/docker,docker/docker,jameszhan/docker,nawawi/docker,vdemeester/docker,ripcurld0/moby,tophj-ibm/docker,shishir-a412ed/docker,vdemeester/docker,dmcgowan/docker,duglin/docker,mixja/docker,flavio/docker,nawawi/docker,ibuildthecloud/docker,tophj-ibm/moby,docker/docker,crosbymichael/docker,cpuguy83/docker,dims/docker,rremer/moby,jvanz/docker,justincormack/docker,yosifkit/docker,mahak/docker,KarthikNayak/docker,paralin/docker,jlhawn/docker,tophj-ibm/docker,mixja/docker,estesp/docker,noironetworks/docker,shishir-a412ed/docker,scotttlin/docker,laijs/docker,jwhonce/docker,mikebrow/docker,jimjag/docker,dccurtis/docker,tonistiigi/docker,dims/docker,KingEmet/docker,gnailuy/docker,tonistiigi/docker,flavio/docker,KarthikNayak/docker,SvenDowideit/docker,jvanz/docker,noironetworks/docker,AkihiroSuda/docker,pradipd/moby,trebonian/docker,ibuildthecloud/docker,pradipd/moby,scotttlin/docker,maxamillion/docker,docker/docker,tophj-ibm/docker,x1022as/docker,SvenDowideit/docker,moul/docker,moby/moby,jameszhan/docker,estesp/docker,Ramzec/docker,YuPengZTE/docker,dmcgowan/docker,rancher/docker,duglin/docker,mikebrow/docker,nawawi/docker,Mokolea/docker,Ramzec/docker,rancher/docker,estesp/docker,x1022as/docker,yosifkit/docker,konstruktoid/docker-upstream,unclejack/docker,thaJeztah/docker,djs55/docker,dims/docker,kolyshkin/docker,paralin/docker,bearstech/moby,konstruktoid/docker-upstream,mikebrow/docker,kojiromike/docker,justincormack/docker,moby/moby,flavio/docker,nalind/docker,ripcurld0/moby,maxamillion/docker,moul/docker,kojiromike/docker,laijs/docker,SvenDowideit/docker,yosifkit/docker,laijs/moby,bearstech/moby,yosifkit/docker,YuPengZTE/docker,cpuguy83/docker,duglin/docker,AkihiroSuda/docker,kojiromike/docker,thaJeztah/docker,Ramzec/docker,nalind/docker,trebonian/docker,flavio/docker,yongtang/docker,konstruktoid/docker-upstream,tophj-ibm/moby,tonistiigi/docker,whuwxl/docker,bearstech/moby,trebonian/docker,unclejack/docker,KingEmet/docker,allencloud/docker,srust/docker,mahak/docker,whuwxl/docker,rhatdan/docker,konstruktoid/docker-1,djs55/docker,Mokolea/docker,laijs/moby,johnstep/moby-moby,jimjag/docker,yongtang/docker,vdemeester/docker,nawawi/docker,moby/moby,noironetworks/docker,tophj-ibm/moby,srust/docker,srust/docker,gnailuy/docker,Ramzec/docker,rremer/moby,kolyshkin/moby,thaJeztah/docker,jlhawn/docker,gnailuy/docker,cpuguy83/docker,jwhonce/docker,maxamillion/docker,paralin/docker,jthelin/docker,Mokolea/docker,yongtang/docker,jwhonce/docker,ibuildthecloud/docker,jameszhan/docker,KingEmet/docker,crosbymichael/docker,nalind/docker,jimjag/docker,dccurtis/docker,ibuildthecloud/docker,tmp6154/docker,tmp6154/docker,rremer/moby,paralin/docker,crosbymichael/docker,moul/docker,pradipd/moby,johnstep/moby-moby,gnailuy/docker,mixja/docker,allencloud/docker,tmp6154/docker,kolyshkin/moby,dmcgowan/docker,laijs/docker,x1022as/docker,bearstech/moby,whuwxl/docker,unclejack/docker,thaJeztah/docker,dccurtis/docker,rancher/docker,jimjag/docker,jlhawn/docker,laijs/moby,moby/moby,kolyshkin/docker,YuPengZTE/docker,jthelin/docker,mahak/docker,AkihiroSuda/docker,johnstep/moby-moby,kolyshkin/moby,trebonian/docker,KarthikNayak/docker,shishir-a412ed/docker,AkihiroSuda/docker,konstruktoid/docker-1,mahak/docker,konstruktoid/docker-upstream,ripcurld0/moby,allencloud/docker,moul/docker,rhatdan/docker,cpuguy83/docker,djs55/docker,rhatdan/docker,jvanz/docker,konstruktoid/docker-1,scotttlin/docker