Alter PostgresAdmin.prep_data_directory to remove all contents

This will allow us to use it for reinitializing a database server
as a standby when it was previously a primary.

https://bugzilla.redhat.com/show_bug.cgi?id=1426769

lib/gems/pending/util/postgres_admin.rb

@@ -93,8 +93,7 @@ def self.prep_data_directory
     # initdb will fail if the database directory is not empty or not owned by the PostgresAdmin.user
     FileUtils.mkdir(PostgresAdmin.data_directory) unless Dir.exist?(PostgresAdmin.data_directory)
     FileUtils.chown_R(PostgresAdmin.user, PostgresAdmin.user, PostgresAdmin.data_directory)
-    FileUtils.rm_rf(PostgresAdmin.data_directory.join("pg_log"))
-    FileUtils.rm_rf(PostgresAdmin.data_directory.join("lost+found"))
+    FileUtils.rm_rf(PostgresAdmin.data_directory.children.map(&:to_s))
   end
 
   def self.backup(opts)