[posix-app] map log level with syslog (#3133)
[posix-app] map log level with syslog (#3133)


turon/openthread,abtink/openthread,jwhui/openthread,librasungirl/openthread,gandreello/openthread,openthread/openthread,chshu/openthread,bukepo/openthread,chshu/openthread,srickardti/openthread,erja-gp/openthread,LeZhang2016/openthread,turon/openthread,librasungirl/openthread,chshu/openthread,bukepo/openthread,chshu/openthread,lanyuwen/openthread,erja-gp/openthread,librasungirl/openthread,chshu/openthread,abtink/openthread,LeZhang2016/openthread,bukepo/openthread,lanyuwen/openthread,gandreello/openthread,openthread/openthread,LeZhang2016/openthread,erja-gp/openthread,turon/openthread,jwhui/openthread,abtink/openthread,srickardti/openthread,LeZhang2016/openthread,lanyuwen/openthread,srickardti/openthread,jwhui/openthread,gandreello/openthread,gandreello/openthread,openthread/openthread,jwhui/openthread,chshu/openthread,LeZhang2016/openthread,erja-gp/openthread,srickardti/openthread,erja-gp/openthread,lanyuwen/openthread,LeZhang2016/openthread,librasungirl/openthread,lanyuwen/openthread,lanyuwen/openthread,gandreello/openthread,openthread/openthread,bukepo/openthread,gandreello/openthread,erja-gp/openthread,turon/openthread,abtink/openthread