xpack plugin can be isolated now that we have xpack extension support
xpack plugin can be isolated now that we have xpack extension support

Original commit: elastic/x-pack-elasticsearch@9f742c754f084976c11d646749828009a705a003

scorpionvicky/elasticsearch,strapdata/elassandra,gfyoung/elasticsearch,vroyer/elassandra,vroyer/elassandra,HonzaKral/elasticsearch,scorpionvicky/elasticsearch,robin13/elasticsearch,gfyoung/elasticsearch,scorpionvicky/elasticsearch,HonzaKral/elasticsearch,gfyoung/elasticsearch,uschindler/elasticsearch,strapdata/elassandra,GlenRSmith/elasticsearch,GlenRSmith/elasticsearch,robin13/elasticsearch,coding0011/elasticsearch,GlenRSmith/elasticsearch,uschindler/elasticsearch,gingerwizard/elasticsearch,coding0011/elasticsearch,gingerwizard/elasticsearch,gingerwizard/elasticsearch,HonzaKral/elasticsearch,gingerwizard/elasticsearch,strapdata/elassandra,uschindler/elasticsearch,nknize/elasticsearch,gfyoung/elasticsearch,coding0011/elasticsearch,GlenRSmith/elasticsearch,gingerwizard/elasticsearch,robin13/elasticsearch,scorpionvicky/elasticsearch,robin13/elasticsearch,coding0011/elasticsearch,GlenRSmith/elasticsearch,nknize/elasticsearch,robin13/elasticsearch,scorpionvicky/elasticsearch,coding0011/elasticsearch,nknize/elasticsearch,gingerwizard/elasticsearch,gingerwizard/elasticsearch,uschindler/elasticsearch,nknize/elasticsearch,HonzaKral/elasticsearch,uschindler/elasticsearch,vroyer/elassandra,nknize/elasticsearch,strapdata/elassandra,gfyoung/elasticsearch,strapdata/elassandra