Match Stackable nodes on OS label rather than Arch (#100)

See stackabletech/issues#115

Author: nightkr

modules/ROOT/pages/getting_started.adoc

@@ -290,7 +290,7 @@ We will deploy 3 Apache ZooKeeper instances to our cluster. This is a fairly typ
  default:
  selector:
  matchLabels:
- kubernetes.io/arch: stackable-linux
+ kubernetes.io/os: stackable-linux
  replicas: 3
  config:
  adminPort: 12000
@@ -323,7 +323,7 @@ We will deploy 3 Apache Kafka brokers, another typical deployment pattern for Ka
  default:
  selector:
  matchLabels:
- kubernetes.io/arch: stackable-linux
+ kubernetes.io/os: stackable-linux
  replicas: 3
  config:
  logDirs: "/tmp/kafka-logs"
@@ -351,7 +351,7 @@ We will deploy 3 Apache servers NiFi. This might seem over the top for a tutoria
  default:
  selector:
  matchLabels:
- kubernetes.io/arch: stackable-linux
+ kubernetes.io/os: stackable-linux
  replicas: 3
  config:
  nifiWebHttpPort: 10000