Clear 'ctools_plugins' static cache on ctools_get_plugins_reset()

I noticed some strange behaviour on the contexts tab in the page manager, where I had hundreds of contexts and relations with the same name. It took me a while to find the problem. In ctools_get_plugins() two static caches('ctools_plugin_setup' and 'ctools_plugins') are used for loading and building the plugins. This function is actually called twice on the page in ctools_context_handler_edit_context() (once in ctools_context_admin_includes() and once in ctools_context_add_context_form() for contexts). During this process a default view caused a ctools_get_plugins_reset() call on my website.
But in ctools_get_plugins_reset() only the 'ctools_plugin_setup' static variable is cleared, meaning that the second time the function is called, all plugin information is again appended to the 'ctools_plugins' var, leading to incorrect data.