Fix logic governing DataRequest PollTimer. (#1192)
Fix logic governing DataRequest PollTimer. (#1192)

* Plug holes in logic governing the DataRequest PollTimer.

* Free message using message method.

erja-gp/openthread,JakubBrachTieto/openthread,gandreello/openthread,LeZhang2016/openthread,GiedriusM/openthread,turon/openthread,vaas-krish/openthread,abtink/openthread,JakubBrachTieto/openthread,jwhui/openthread,srickardti/openthread,erja-gp/openthread,LeZhang2016/openthread,LeZhang2016/openthread,vaas-krish/openthread,fbsder/openthread,bukepo/openthread,erja-gp/openthread,jjlee3/openthread,turon/openthread,chshu/openthread,aeliot/openthread,pvanhorn/openthread,xiaom-GitHub/openthread,gandreello/openthread,nibanks/openthread,librasungirl/openthread,gandreello/openthread,nibanks/openthread,mszczodrak/openthread,lanyuwen/openthread,aeliot/openthread,pvanhorn/openthread,fbsder/openthread,lanyuwen/openthread,vaas-krish/openthread,chshu/openthread,georgecpr/openthread,xiaom-GitHub/openthread,librasungirl/openthread,nibanks/openthread,JakubBrachTieto/openthread,JakubBrachTieto/openthread,jwhui/openthread,erja-gp/openthread,bukepo/openthread,Zolertia/openthread,chshu/openthread,fbsder/openthread,mszczodrak/openthread,mszczodrak/openthread,chshu/openthread,lanyuwen/openthread,openthread/openthread,gandreello/openthread,srickardti/openthread,jjlee9/openthread,Zolertia/openthread,aeliot/openthread,GiedriusM/openthread,georgecpr/openthread,georgecpr/openthread,xiaom-GitHub/openthread,jjlee9/openthread,gandreello/openthread,jjlee9/openthread,Zolertia/openthread,nibanks/openthread,erja-gp/openthread,jjlee3/openthread,srickardti/openthread,LeZhang2016/openthread,jjlee3/openthread,turon/openthread,JakubBrachTieto/openthread,mszczodrak/openthread,pvanhorn/openthread,fbsder/openthread,openthread/openthread,vaas-krish/openthread,GiedriusM/openthread,georgecpr/openthread,mszczodrak/openthread,jjlee9/openthread,xiaom-GitHub/openthread,jwhui/openthread,jjlee9/openthread,Zolertia/openthread,srickardti/openthread,aeliot/openthread,librasungirl/openthread,erja-gp/openthread,openthread/openthread,fbsder/openthread,georgecpr/openthread,bukepo/openthread,aeliot/openthread,pvanhorn/openthread,jjlee9/openthread,mszczodrak/openthread,lanyuwen/openthread,jjlee3/openthread,turon/openthread,nibanks/openthread,vaas-krish/openthread,JakubBrachTieto/openthread,vaas-krish/openthread,openthread/openthread,librasungirl/openthread,bukepo/openthread,chshu/openthread,GiedriusM/openthread,lanyuwen/openthread,xiaom-GitHub/openthread,xiaom-GitHub/openthread,aeliot/openthread,lanyuwen/openthread,abtink/openthread,georgecpr/openthread,GiedriusM/openthread,abtink/openthread,LeZhang2016/openthread,pvanhorn/openthread,abtink/openthread,nibanks/openthread,fbsder/openthread,jjlee3/openthread,LeZhang2016/openthread,chshu/openthread,Zolertia/openthread,jwhui/openthread,gandreello/openthread,pvanhorn/openthread