Fix warning when cloning repo that already exists

fixes the warning:

fatal: destination path '~/gitlab-ce/gitlab/tmp/tests/gitlab-test-fork_bare' already exists and is not an empty directory.

spec/support/test_env.rb

@@ -131,9 +131,11 @@ module TestEnv
 
     set_repo_refs(repo_path, branch_sha)
 
+    unless File.directory?(repo_path_bare)
       # We must copy bare repositories because we will push to them.
       system(git_env, *%W(#{Gitlab.config.git.bin_path} clone -q --bare #{repo_path} #{repo_path_bare}))
     end
+  end
 
   def copy_repo(project)
     base_repo_path = File.expand_path(factory_repo_path_bare)