Do not delete the SQL dump too early

The change in baa15792 broke backup
restore fucnctionality. This would not lead to data loss, but it
prevented the restore script from working. This bug exists only in
7.14.0 release candidate versions, not in 7.13.

Reported in https://github.com/gitlabhq/gitlabhq/issues/9571 .

lib/backup/database.rb

@@ -7,14 +7,15 @@ module Backup
     def initialize
       @config = YAML.load_file(File.join(Rails.root,'config','database.yml'))[Rails.env]
       @db_dir = File.join(Gitlab.config.backup.path, 'db')
+    end
+
+    def dump
       FileUtils.rm_rf(@db_dir)
       # Ensure the parent dir of @db_dir exists
       FileUtils.mkdir_p(Gitlab.config.backup.path)
       # Fail if somebody raced to create @db_dir before us
       FileUtils.mkdir(@db_dir, mode: 0700)
-    end
 
-    def dump
       success = case config["adapter"]
       when /^mysql/ then
         $progress.print "Dumping MySQL database #{config['database']} ... "