Allow setting state for backend packages

A user might want the latest copy or the backend DB packages not
installed at all if installing in a venv.

Change-Id: I811bc71c604c37b3be3ca2ef7c71d54ef40a1830

manifests/db.pp

@@ -19,6 +19,11 @@
 #   (Optional) The back end to use for the database.
 #   Defaults to $::os_service_default
 #
+# [*backend_package_ensure*]
+#   (Optional) Desired ensure state of the backend database package,
+#   accepts latest or specific versions.
+#   Defaults to present.
+#
 # [*connection*]
 #   (Optional) The SQLAlchemy connection string to use to connect to the database.
 #   Defaults to $::os_service_default
@@ -99,6 +104,7 @@ define oslo::db(
   $sqlite_db              = $::os_service_default,
   $sqlite_synchronous     = $::os_service_default,
   $backend                = $::os_service_default,
+  $backend_package_ensure = present,
   $connection             = $::os_service_default,
   $slave_connection       = $::os_service_default,
   $mysql_sql_mode         = $::os_service_default,
@@ -153,7 +159,7 @@ define oslo::db(
 
     if $backend_package and !defined(Package[$backend_package]) {
       package { 'db_backend_package':
-        ensure => present,
+        ensure => $backend_package_ensure,
         name   => $backend_package,
         tag    => 'openstack',
       }

releasenotes/notes/backend_package_ensure-54b4525895ce9acd.yaml

@@ -0,0 +1,6 @@
+---
+features:
+  - Allow setting the desired state of the backend
+    database package. This will default to present
+    which maintains original behavior but allows
+    for more flexibility.