Fix expiration checking. (follows 9baf378 in 2.0)
Fix expiration checking. (follows 9baf378 in 2.0)

Adveez/node-oauth2-server,maxtruxa/node-oauth2-server,kiddkai/node-oauth2-server,awatson1978/node-oauth2-server,systeminsights/node-oauth2-server,sjava9s/node-oauth2-server,razvanz/node-oauth2-server,shawnpage/node-oauth2-server,tonymrakovcic/node-oauth2-server,lancecarlson/node-oauth2-server,ashishkrishnan/node-oauth2-server,inthepocket/node-oauth2-server,jimtang9527/minicloud-node-oauth2-server,minicloud/minicloud-node-oauth2-server,marsanla/node-oauth2-server-restify,nooks/node-oauth2-server,zipongo/node-oauth2-server,Gp2mv3/node-oauth2-server,SuperAwesomeLTD/node-oauth2-server,oauthjs/node-oauth2-server,visvk/node-oauth2-server,guillaumehilaire/node-oauth2-server,manjeshpv/node-oauth2-server,mjsalinger/node-oauth2-server,Crocagile/node-oauth2-server,stefankolling/node-oauth2-server,Sjaakmoes/node-oauth2-server-restify,seegno-forks/node-oauth2-server,thomseddon/node-oauth2-server,bstouffer/node-oauth2-server,spark/node-oauth2-server,jakehafdahl/node-oauth2-server,Mediahead-AG/node-oauth2-server,octoblu/node-oauth2-server,konder/node-oauth2-server,zoltangbereczky/node-oauth2-server,jdjkelly/node-oauth2-server