Fix thread safety of SelinuxEnabled and getSelinuxMountPoint
Fix thread safety of SelinuxEnabled and getSelinuxMountPoint

Both suffered from different race conditions.

SelinuxEnabled assigned selinuxEnabledChecked before selinuxEnabled.
Thus racing callers could see the wrong selinuxEnabled.

getSelinuxMountPoint assigned selinuxfs to "" before it know the right
value. Thus racing could see "" improperly.

The gate selinuxfs, enabled, and mclist all on the same lock

xiaochenshen/runc,maxamillion/runc,crosbymichael/runc,adrianreber/runc,crosbymichael/runc,rhatdan/runc,mheon/runc,avagin/runc,hqhq/runc,sunyuan3/runc,docker/runc,xiaochenshen/runc,dqminh/runc,justincormack/runc,jhowardmsft/runc,rhatdan/runc,opencontainers/runc,xiaochenshen/runc,cloudfoundry-incubator/runc,coolljt0725/runc,cyphar/runc,shishir-a412ed/runc,dqminh/runc,estesp/runc,vbatts/runc,adrianreber/runc,kolyshkin/runc,vbatts/runc,rajasec/runc,WeiZhang555/runc,mYmNeo/runc,dqminh/runc,mYmNeo/runc,mheon/runc,opencontainers/runc,rhatdan/runc,shishir-a412ed/runc,mYmNeo/runc,opencontainers/runc,WeiZhang555/runc,sunyuan3/runc,maxamillion/runc,mikebrow/runc,wking/runc,WeiZhang555/runc,coolljt0725/runc,hqhq/runc,crosbymichael/runc,kolyshkin/runc,stefanberger/runc,dqminh/runc,laijs/runc,jhowardmsft/runc,shishir-a412ed/runc,vbatts/runc,wking/runc,laijs/runc,cloudfoundry-incubator/runc,cyphar/runc,hqhq/runc,cyphar/runc,cloudfoundry-incubator/runc,kolyshkin/runc,rhatdan/runc,rajasec/runc,kolyshkin/runc,sunyuan3/runc,estesp/runc,wking/runc,justincormack/runc,docker/runc,rajasec/runc,laijs/runc,avagin/runc,stefanberger/runc,stefanberger/runc,maxamillion/runc,jhowardmsft/runc,adrianreber/runc,justincormack/runc,mikebrow/runc,docker/runc,opencontainers/runc,mikebrow/runc,mheon/runc,coolljt0725/runc,estesp/runc,avagin/runc