[SwarmCluster] Add RLock to Cluster.hasEngine
[SwarmCluster] Add RLock to Cluster.hasEngine

Signed-off-by: Anton Tiurin <b91bf98aa7cea39040737992640d61c368ae17fe@yandex.ru>

affo/swarm,ch3lo/swarm,joaofnfernandes/docker.github.io,anweiss/docker.github.io,tranceitionalMynd/swarm,Spritekin/swarm,aduermael/docker.github.io,troy0820/docker.github.io,linecheng/swarm,gradywang/swarm,CiaranCostello/swarm,rav121/swarm,jimenez/swarm,mavenugo/swarm,ezrasilvera/swarm,abronan/swarm,schmunk42/swarm,errordeveloper/swarm,londoncalling/docker.github.io,barais/swarm,shahankhatch/swarm,rchicoli/swarm,alexisbellido/docker.github.io,mrjana/swarm,LuisBosquez/docker.github.io,docker-zh/docker.github.io,shot/swarm,liubin/swarm,unodba/swarm,jzwlqx/denverdino.github.io,denverdino/swarm,kunalkushwaha/swarm,EderRoger/swarm,yp-engineering/swarm,moxiegirl/swarm,phiroict/docker,therealbill/swarm,EderRoger/swarm,jay-lau/swarm,LukasBacigal/swarm,docker/docker.github.io,ejholmes/swarm,CiaranCostello/swarm,joeuo/docker.github.io,riuvshin/swarm,bpradipt/swarm,gdevillele/docker.github.io,docker-zh/docker.github.io,snrism/swarm,mavenugo/swarm,beni55/swarm-1,resouer/swarm,xFragger/swarm,raoofm/swarm,JimGalasyn/docker.github.io,aduermael/docker.github.io,kunalkushwaha/swarm,ch3lo/swarm,dims/swarm,phiroict/docker,gdevillele/docker.github.io,danix800/docker.github.io,kyhavlov/swarm,zkcrescent/swarm,tangkun75/swarm,johnstep/docker.github.io,snrism/swarm,therealbill/swarm,swarm-hooks/swarm,joeuo/docker.github.io,danix800/docker.github.io,jimmyxian/swarm,menglingwei/denverdino.github.io,rillig/docker.github.io,parapsyche/swarm,joeuo/docker.github.io,denverdino/swarm,dims/swarm,docker/docker.github.io,francisbouvier/swarm,rillig/docker.github.io,shin-/docker.github.io,ricca742/swarm,atlassian/swarm,sanscontext/docker.github.io,Aorjoa/swarm,denverdino/docker.github.io,krystism/swarm,thaJeztah/docker.github.io,menglingwei/denverdino.github.io,megamsys/swarm,tangkun75/swarm,jdamick/swarm,allencloud/swarm,BSWANG/denverdino.github.io,schmunk42/swarm,auzias/swarm,shubheksha/docker.github.io,docker/docker.github.io,menglingwei/denverdino.github.io,cgvarela/swarm,bpradipt/swarm,tranceitionalMynd/swarm,joeuo/docker.github.io,londoncalling/docker.github.io,sfsmithcha/swarm,CodeNow/swarm,shin-/docker.github.io,docker/docker.github.io,BSWANG/denverdino.github.io,CodeNow/swarm,abronan/swarm,resouer/swarm,phiroict/docker,jdamick/swarm,denverdino/docker.github.io,bdwill/docker.github.io,FollowMyDev/swarm,denverdino/denverdino.github.io,anweiss/docker.github.io,swarm-hooks/swarm,londoncalling/docker.github.io,pssahi/swarm,bdwill/docker.github.io,sanscontext/docker.github.io,BSWANG/denverdino.github.io,sanscontext/docker.github.io,menglingwei/denverdino.github.io,adouang/swarm,JimGalasyn/docker.github.io,LuisBosquez/docker.github.io,u2mejc/swarm,pssahi/swarm,anweiss/docker.github.io,mgoelzer/swarm,christophelec/swarm,bsmr-docker/swarm,rillig/docker.github.io,aduermael/docker.github.io,FreedomWangLi/swarm,Spritekin/swarm,errordeveloper/swarm,everett-toews/swarm,morpheyesh/swarm,vlajos/swarm,troy0820/docker.github.io,MHBauer/swarm,ehazlett/swarm,kyhavlov/swarm,shahankhatch/swarm,srikalyan/swarm,echupriyanov/swarm,Aorjoa/swarm,LuisBosquez/docker.github.io,rancher/swarm,denverdino/denverdino.github.io,sfsmithcha/swarm,docker-zh/docker.github.io,LukasBacigal/swarm,pdevine/swarm,thaJeztah/docker.github.io,u2mejc/swarm,ezrasilvera/swarm,FollowMyDev/swarm,jay-lau/swarm,shubheksha/docker.github.io,bdwill/docker.github.io,ricca742/swarm,bsmr-docker/swarm,LuisBosquez/docker.github.io,phiroict/docker,mrjana/swarm,jzwlqx/denverdino.github.io,rutulpatel/swarm,deis/swarm,denverdino/swarm-1,jzwlqx/denverdino.github.io,denverdino/docker.github.io,BSWANG/denverdino.github.io,auzias/swarm,moxiegirl/swarm,gdevillele/docker.github.io,jimmycmh/swarm,ealang/swarm,doronp/swarm,gradywang/swarm,PeoplePerHour/libswarm,ezrasilvera/SwarmACLs,christophelec/swarm,everett-toews/swarm,akerbis/armhf-swarm,atlassian/swarm,gonkulator/swarm,yp-engineering/swarm,qianzhangxa/swarm,jeffjen/swarm,johnstep/docker.github.io,jzwlqx/denverdino.github.io,johnstep/docker.github.io,dnephin/swarm,shot/swarm,NunoEdgarGub1/swarm,BSWANG/denverdino.github.io,alexisbellido/docker.github.io,alexisbellido/docker.github.io,xFragger/swarm,rutulpatel/swarm,PeoplePerHour/libswarm,echupriyanov/swarm,denverdino/denverdino.github.io,menglingwei/denverdino.github.io,gdevillele/docker.github.io,beni55/swarm-1,iaintshine/swarm,FreedomWangLi/swarm,JimGalasyn/docker.github.io,vlajos/swarm,johnstep/docker.github.io,polyverse-security/swarm,troy0820/docker.github.io,riuvshin/swarm,docker-zh/docker.github.io,pdevine/swarm,jimmyxian/swarm,alexisbellido/docker.github.io,cgvarela/swarm,dnephin/swarm,sanscontext/docker.github.io,joaofnfernandes/docker.github.io,iaintshine/swarm,denverdino/docker.github.io,rajdeepd/swarm,shubheksha/docker.github.io,BSWANG/swarm,BSWANG/swarm,akerbis/armhf-swarm,joeuo/docker.github.io,joaofnfernandes/docker.github.io,raoofm/swarm,deis/swarm,rav121/swarm,docker-zh/docker.github.io,johnstep/docker.github.io,cpuguy83/swarm,danix800/docker.github.io,thaJeztah/docker.github.io,sansconte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