[TEST] bumps rolling upgrade bwc version to 5.4.0-snapshot
[TEST] bumps rolling upgrade bwc version to 5.4.0-snapshot

Original commit: elastic/x-pack-elasticsearch@2f321682d23914fc0ee72834137725ab1a06ef4b

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