[Watcher] Use auto_expand_replicas on triggered_watches index too (elastic/x-pack-elasticsearch#3371)
[Watcher] Use auto_expand_replicas on triggered_watches index too (elastic/x-pack-elasticsearch#3371)

In the previous pass, only the ".watch*" templates were impacted. This also should use `auto_expand_replicas`.

Original commit: elastic/x-pack-elasticsearch@5d3a4f1f7bc3eed16a0d3517aafdf9b4fb6c0f90

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