[netif] initialize mIsUp (#2393)
[netif] initialize mIsUp (#2393)


chshu/openthread,librasungirl/openthread,gandreello/openthread,pvanhorn/openthread,mszczodrak/openthread,xiaom-GitHub/openthread,georgecpr/openthread,gandreello/openthread,openthread/openthread,jwhui/openthread,srickardti/openthread,LeZhang2016/openthread,georgecpr/openthread,lanyuwen/openthread,pvanhorn/openthread,chshu/openthread,abtink/openthread,mszczodrak/openthread,pvanhorn/openthread,abtink/openthread,bukepo/openthread,erja-gp/openthread,xiaom-GitHub/openthread,erja-gp/openthread,LeZhang2016/openthread,lanyuwen/openthread,chshu/openthread,LeZhang2016/openthread,gandreello/openthread,chshu/openthread,lanyuwen/openthread,bukepo/openthread,bukepo/openthread,mszczodrak/openthread,erja-gp/openthread,erja-gp/openthread,librasungirl/openthread,jwhui/openthread,xiaom-GitHub/openthread,librasungirl/openthread,gandreello/openthread,mszczodrak/openthread,openthread/openthread,openthread/openthread,jwhui/openthread,xiaom-GitHub/openthread,srickardti/openthread,librasungirl/openthread,georgecpr/openthread,lanyuwen/openthread,turon/openthread,jwhui/openthread,erja-gp/openthread,LeZhang2016/openthread,LeZhang2016/openthread,georgecpr/openthread,bukepo/openthread,pvanhorn/openthread,mszczodrak/openthread,turon/openthread,LeZhang2016/openthread,georgecpr/openthread,pvanhorn/openthread,erja-gp/openthread,openthread/openthread,turon/openthread,chshu/openthread,gandreello/openthread,xiaom-GitHub/openthread,lanyuwen/openthread,lanyuwen/openthread,abtink/openthread,srickardti/openthread,georgecpr/openthread,mszczodrak/openthread,srickardti/openthread,turon/openthread,chshu/openthread,xiaom-GitHub/openthread,abtink/openthread,pvanhorn/openthread,gandreello/openthread