Fix the update check status message showing up twice when two plugins are using the library.
Fix the update check status message showing up twice when two plugins are using the library.

Pass the plugin slug in a separate "puc_slug" query parameter when doing a manual update check. This way displayManualCheckResult() can verify that the current "puc_update_check_result" value applies to the right plugin.

adigital/plugin-update-checker,adigital/plugin-update-checker,YahnisElsts/plugin-update-checker,YahnisElsts/plugin-update-checker