Mark the import as failed if a temporary or unknown error happened.

I've seen some users have reported that the updated of their mirror
repositories is being stuck, it basically happens because a temporary or
unknown error happened and the import status was kept in `started`
instead of being marked as `failed`.

app/workers/repository_update_mirror_worker.rb

@@ -25,7 +25,7 @@ class RepositoryUpdateMirrorWorker
 
       project.import_finish
     rescue => ex
-      project.mark_import_as_failed("We're sorry, a temporary error happened, please try again.")
+      project.mark_import_as_failed("We're sorry, a temporary error occurred, please try again.")
 
       raise UpdateMirrorError, "#{ex.class}: #{ex.message}"
     end

app/workers/repository_update_remote_mirror_worker.rb

@@ -19,7 +19,7 @@ class RepositoryUpdateRemoteMirrorWorker
         remote_mirror.update_finish
       end
     rescue => ex
-      remote_mirror.mark_as_failed("We're sorry, a temporary error happened, please try again.")
+      remote_mirror.mark_as_failed("We're sorry, a temporary error occurred, please try again.")
 
       raise UpdateRemoteMirrorError, "#{ex.class}: #{ex.message}"
     end