[lowpan] fix uninitialized variable warnings (#2126)
[lowpan] fix uninitialized variable warnings (#2126)


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