Kill create_cluster pillar switch, refs: #100

It is just a variant of init_db. A more correct solution would be to
support configuring a different initdb command while passing values from
the pillar by default like version. This would make it truly generic but
is probably not achievable given current pillar self-referencing
capabilities (ie. none).

Thus, I decided to make it OS family specific since Debian provides its
own tools to manage clusters, etc. Gentoo also has a specific way to
initialize a new cluster which does not fit with commands.initdb so
the current if/elif would be extended when support is added for Gentoo.

postgres/osmap.yaml

@@ -1,8 +1,7 @@
 RedHat:
-  init_db: True
+  initdb_user: postgres
   commands:
     initdb: initdb
-  initdb_user: postgres
   pkg: postgresql-server
   pkg_client: postgresql
   pkg_repo: pgdg94
@@ -10,7 +9,6 @@ RedHat:
 Arch:
   conf_dir: /var/lib/postgres/data
   data_dir: /var/lib/postgres/data
-  init_db: True
   initdb_user: postgres
   commands:
     initdb: initdb --locale en_US.UTF8 -E UTF8 -D "/var/lib/postgres/data"
@@ -19,11 +17,11 @@ Arch:
 Debian:
   pkg_repo_file: /etc/apt/sources.list.d/pgdg.list
   pkg_libpq_dev: libpq-dev
+  initdb: False
 Suse:
-  init_db: True
+  initdb_user: postgres
   commands:
     initdb: initdb
-  initdb_user: postgres
   pkg: postgresql-server
   pkg_client: postgresql
 FreeBSD: