file backend: do not inherit from glance::api

Do not make ::glance::backend::file inherits from ::glance::api because
::glance::api has parameters.
The class was broken until now.

Also, we need to include glance::backend::file to have
'filesystem_store_datadir' parameter in Glance config, since we're using
file backend.

If you don't provide this parameter, Glance fails to start:
glance_store._drivers.filesystem [-] Specify at least
'filesystem_store_datadir' or 'filesystem_store_datadirs' option

Change-Id: Iba6791199f7a2c7fef24b1e8752ed0b564b8512f

manifests/backend/file.pp

@@ -11,7 +11,7 @@
 #
 class glance::backend::file(
   $filesystem_store_datadir = '/var/lib/glance/images/'
-) inherits glance::api {
+) {
 
   glance_api_config {
     'glance_store/default_store':            value => 'file';

spec/acceptance/basic_glance_spec.rb

@@ -73,6 +73,7 @@ describe 'glance class' do
       # Glance resources
       include ::glance
       include ::glance::client
+      include ::glance::backend::file
       class { '::glance::db::mysql':
         # https://bugs.launchpad.net/puppet-glance/+bug/1446375
         collate  => 'utf8_general_ci',

spec/classes/glance_backend_file_spec.rb

@@ -5,10 +5,6 @@ describe 'glance::backend::file' do
     { :osfamily => 'Debian' }
   end
 
-  let :pre_condition do
-    'class { "glance::api": keystone_password => "pass" }'
-  end
-
   it 'configures glance-api.conf' do
     is_expected.to contain_glance_api_config('glance_store/default_store').with_value('file')
     is_expected.to contain_glance_api_config('glance_store/filesystem_store_datadir').with_value('/var/lib/glance/images/')