Adding etcd username on linux:system level

The patch moves creation of etcd username on linux:system to be
created by linux.system state because of the fact that in salt > 2016.11
behavior of gid_from_name parameter has been changed so currently if
gid_from_name = True and the group doesn't exist then etcd.server.service
will fail.

https://docs.saltstack.com/en/2016.3/ref/states/all/salt.states.user.html
https://docs.saltstack.com/en/2017.7/ref/states/all/salt.states.user.html

Change-Id: Iea3f9811b83ec9239ce2c219ff3ad99fd6cf2ac3
Related-PROD: PROD-20579
Related-PROD: PROD-20581
diff --git a/metadata/service/linux.yml b/metadata/service/linux.yml
new file mode 100644
index 0000000..29127b9
--- /dev/null
+++ b/metadata/service/linux.yml
@@ -0,0 +1,10 @@
+parameters:
+  linux:
+    system:
+      user:
+        etcd:
+          enabled: true
+          name: etcd
+          home: /var/lib/etcd
+          shell: /bin/false
+          system: True