Initialize the key/directory before watching on kv discovery
Initialize the key/directory before watching on kv discovery

Before that change, etcd and zookeeper would fail to instantiate
the discovery without the key being already there in the store or
created beforehand and implicitely by a 'swarm join'.

Signed-off-by: Alexandre Beslic <a2bebfa25877ed8f3a644256dc060dfe32006f27@docker.com>

cpuguy83/swarm,londoncalling/docker.github.io,ezrasilvera/swarm,thaJeztah/docker.github.io,anweiss/docker.github.io,bdwill/docker.github.io,gradywang/swarm,kyhavlov/swarm,BSWANG/denverdino.github.io,denverdino/denverdino.github.io,JimGalasyn/docker.github.io,MHBauer/swarm,dnephin/swarm,schmunk42/swarm,denverdino/denverdino.github.io,LuisBosquez/docker.github.io,menglingwei/denverdino.github.io,troy0820/docker.github.io,megamsys/swarm,sanscontext/docker.github.io,linecheng/swarm,BSWANG/swarm,swarm-hooks/swarm,alexisbellido/docker.github.io,bdwill/docker.github.io,bsmr-docker/swarm,allencloud/swarm,menglingwei/denverdino.github.io,echupriyanov/swarm,xFragger/swarm,thaJeztah/docker.github.io,LuisBosquez/docker.github.io,joaofnfernandes/docker.github.io,sanscontext/docker.github.io,moxiegirl/swarm,denverdino/swarm,jzwlqx/denverdino.github.io,xFragger/swarm,danix800/docker.github.io,docker/docker.github.io,shubheksha/docker.github.io,JimGalasyn/docker.github.io,johnstep/docker.github.io,danix800/docker.github.io,kunalkushwaha/swarm,phiroict/docker,johnstep/docker.github.io,allencloud/swarm,LuisBosquez/docker.github.io,schmunk42/swarm,jzwlqx/denverdino.github.io,JimGalasyn/docker.github.io,moxiegirl/swarm,fugr/swarm,shin-/docker.github.io,Spritekin/swarm,docker/docker.github.io,docker-zh/docker.github.io,morpheyesh/swarm,BSWANG/denverdino.github.io,sanscontext/docker.github.io,resouer/swarm,morpheyesh/swarm,gdevillele/docker.github.io,BSWANG/denverdino.github.io,doronp/swarm,docker-zh/docker.github.io,rancher/swarm,troy0820/docker.github.io,fugr/swarm,barais/swarm,alexisbellido/docker.github.io,rchicoli/swarm,qianzhangxa/swarm,auzias/swarm,atlassian/swarm,mgoelzer/swarm,jimmycmh/swarm,alexisbellido/docker.github.io,shubheksha/docker.github.io,alexisbellido/docker.github.io,BSWANG/denverdino.github.io,denverdino/denverdino.github.io,gdevillele/docker.github.io,joeuo/docker.github.io,docker-zh/docker.github.io,joeuo/docker.github.io,rillig/docker.github.io,phiroict/docker,denverdino/denverdino.github.io,docker/docker.github.io,barais/swarm,BSWANG/denverdino.github.io,aduermael/docker.github.io,alexisbellido/docker.github.io,jzwlqx/denverdino.github.io,JimGalasyn/docker.github.io,shin-/docker.github.io,rillig/docker.github.io,LuisBosquez/docker.github.io,liubin/swarm,cpuguy83/swarm,ezrasilvera/swarm,bdwill/docker.github.io,shubheksha/docker.github.io,londoncalling/docker.github.io,ch3lo/swarm,joaofnfernandes/docker.github.io,docker-zh/docker.github.io,mgoelzer/swarm,johnstep/docker.github.io,menglingwei/denverdino.github.io,joeuo/docker.github.io,MHBauer/swarm,bdwill/docker.github.io,gdevillele/docker.github.io,dnephin/swarm,gdevillele/docker.github.io,ch3lo/swarm,docker/docker.github.io,menglingwei/denverdino.github.io,londoncalling/docker.github.io,riuvshin/swarm,megamsys/swarm,londoncalling/docker.github.io,CodeNow/swarm,atlassian/swarm,qianzhangxa/swarm,sanscontext/docker.github.io,sanscontext/docker.github.io,gradywang/swarm,rillig/docker.github.io,danix800/docker.github.io,denverdino/docker.github.io,troy0820/docker.github.io,docker/docker.github.io,LuisBosquez/docker.github.io,joaofnfernandes/docker.github.io,thaJeztah/docker.github.io,phiroict/docker,kyhavlov/swarm,auzias/swarm,CiaranCostello/swarm,JimGalasyn/docker.github.io,denverdino/denverdino.github.io,rillig/docker.github.io,CiaranCostello/swarm,jzwlqx/denverdino.github.io,joeuo/docker.github.io,BSWANG/swarm,denverdino/swarm,joaofnfernandes/docker.github.io,shubheksha/docker.github.io,shin-/docker.github.io,thaJeztah/docker.github.io,denverdino/docker.github.io,anweiss/docker.github.io,denverdino/docker.github.io,joaofnfernandes/docker.github.io,rancher/swarm,phiroict/docker,sfsmithcha/swarm,menglingwei/denverdino.github.io,joeuo/docker.github.io,shin-/docker.github.io,resouer/swarm,troy0820/docker.github.io,doronp/swarm,CodeNow/swarm,phiroict/docker,aduermael/docker.github.io,riuvshin/swarm,denverdino/docker.github.io,jimmycmh/swarm,denverdino/docker.github.io,pdevine/swarm,johnstep/docker.github.io,docker-zh/docker.github.io,anweiss/docker.github.io,johnstep/docker.github.io,LukasBacigal/swarm,londoncalling/docker.github.io,linecheng/swarm,bdwill/docker.github.io,bsmr-docker/swarm,pdevine/swarm,jzwlqx/denverdino.github.io,aduermael/docker.github.io,echupriyanov/swarm,shubheksha/docker.github.io,gdevillele/docker.github.io,rchicoli/swarm,aduermael/docker.github.io,swarm-hooks/swarm,Spritekin/swarm,anweiss/docker.github.io,kunalkushwaha/swarm,liubin/swarm,sfsmithcha/swarm,LukasBacigal/swarm,danix800/docker.github.io,thaJeztah/docker.github.io,shin-/docker.github.io,anweiss/docker.github.io