Fix git_worktree checkout with a Pathname

[agrare]

Fix git_repository.checkout with a Pathname in ConfigurationScriptSource#checkout_git_repository

  1) ManageIQ::Providers::EmbeddedTerraform::AutomationManager::ConfigurationScriptSource with a local repo create_in_provider runs sync finds top level template
     Failure/Error:
           checkout_git_repository do |git_checkout_tempdir|
             # traverse through files in git-worktree
             git_repository.with_worktree do |worktree|
               worktree.ref = scm_branch
       
               # Find all dir's with .tf/.tf.json files
               worktree.blob_list
                       .group_by          { |file| File.dirname(file) }
                       .select            { |_dir, files| files.any? { |f| f.end_with?(".tf", ".tf.json") } }
                       .transform_values! { |files| files.map { |f| File.basename(f) } }
     
     MiqException::Error:
       no implicit conversion of Pathname into String
     # /home/grare/adam/src/manageiq/manageiq/app/models/git_repository.rb:222:in `rescue in handling_worktree_errors'
     # /home/grare/adam/src/manageiq/manageiq/app/models/git_repository.rb:217:in `handling_worktree_errors'
     # /home/grare/adam/src/manageiq/manageiq/app/models/git_repository.rb:108:in `with_worktree'
     # /home/grare/adam/src/manageiq/manageiq/app/models/git_repository.rb:87:in `checkout'
     # /home/grare/adam/src/manageiq/manageiq/app/models/manageiq/providers/embedded_automation_manager/configuration_script_source.rb:96:in `checkout_git_repository'
     # ./app/models/manageiq/providers/embedded_terraform/automation_manager/configuration_script_source.rb:79:in `find_templates_in_git_repo'
     # ./app/models/manageiq/providers/embedded_terraform/automation_manager/configuration_script_source.rb:18:in `block in sync'

Fixes ManageIQ/manageiq-providers-embedded_terraform#79 test failures