fix: do not register sub containers to existing sessions if main container is TERMINATED#403

achimnol merged 5 commits intomainlablup/backend.ai-manager:mainfrom

fix/prevent-sgroup-scheduler-fail-when-only-sub-containers-are-runninglablup/backend.ai-manager:fix/prevent-sgroup-scheduler-fail-when-only-sub-containers-are-runningCopy head branch name to clipboard