Reverse the logic for checking for sig expiration
Reverse the logic for checking for sig expiration

vinhhrv/skydns,no2key/skydns,netf/skydns,AdoHe/skydns,tonicbupt/skydns,loveshell/skydns,andrewrothstein/skydns,nicescale/skydns,erimatnor/skydns-kubernetes,yonglehou/skydns,ZeaLoVe/skydns,smarterclayton/skydns,skynetservices/skydns,tuannvm/skydns,zvelo/zvelo-skydns,zhang0137/skydns,hw-qiaolei/skydns,weekface/skydns