Use gitlab_shell.path to invoke rewrite-hooks.sh

The backup restore code for repositories was assuming that gitlab-shell
is installed in /home/git/gitlab-shell. This commit changes that to use
the configuration setting from gitlab.yml that specifies the path where
gitlab-shell is installed.

lib/backup/repository.rb

@@ -72,8 +72,7 @@ module Backup
       end
 
       print 'Put GitLab hooks in repositories dirs'.yellow
-      gitlab_shell_user_home = File.expand_path("~#{Gitlab.config.gitlab_shell.ssh_user}")
-      if system("#{gitlab_shell_user_home}/gitlab-shell/support/rewrite-hooks.sh", Gitlab.config.gitlab_shell.repos_path)
+      if system("#{Gitlab.config.gitlab_shell.path}/support/rewrite-hooks.sh", Gitlab.config.gitlab_shell.repos_path)
         puts " [DONE]".green
       else
         puts " [FAILED]".red