Add preflight check to dynamic mapping updates#48867

DaveCTurner merged 1 commit intoelastic:7.xelastic/elasticsearch:7.xfrom

DaveCTurner:2019-11-05-preflight-mapping-updates-7x-backportDaveCTurner/elasticsearch:2019-11-05-preflight-mapping-updates-7x-backportCopy head branch name to clipboard