Author: David Monllao
MDL-58905 auth_oauth2: Return if no issuers allow login
http://git.moodle.org/gw?p=moodle.git;a=commit;h=56fb39316ff1ea703c2e3bde5a3c4719c9ff8056
http://github.com/moodle/moodle/commit/56fb39316ff1ea703c2e3bde5a3c4719c9ff8056
+ 3.3 en [issuernologin,auth_oauth2]
+ 3.3 en [noissuersavailable,auth_oauth2]