[ncp] allow log/prints while an async property update is pending (#2454)
[ncp] allow log/prints while an async property update is pending (#2454)

This commit changes the `StreamWrite` logic to allow logs/prints
when there is a pending async property update.
bukepo/openthread,pvanhorn/openthread,openthread/openthread,erja-gp/openthread,bukepo/openthread,LeZhang2016/openthread,pvanhorn/openthread,xiaom-GitHub/openthread,LeZhang2016/openthread,openthread/openthread,georgecpr/openthread,gandreello/openthread,mszczodrak/openthread,jwhui/openthread,gandreello/openthread,abtink/openthread,librasungirl/openthread,georgecpr/openthread,lanyuwen/openthread,librasungirl/openthread,pvanhorn/openthread,turon/openthread,jwhui/openthread,erja-gp/openthread,mszczodrak/openthread,gandreello/openthread,erja-gp/openthread,pvanhorn/openthread,mszczodrak/openthread,jwhui/openthread,abtink/openthread,lanyuwen/openthread,bukepo/openthread,mszczodrak/openthread,chshu/openthread,srickardti/openthread,georgecpr/openthread,erja-gp/openthread,librasungirl/openthread,openthread/openthread,mszczodrak/openthread,turon/openthread,lanyuwen/openthread,chshu/openthread,mszczodrak/openthread,turon/openthread,jwhui/openthread,georgecpr/openthread,gandreello/openthread,xiaom-GitHub/openthread,srickardti/openthread,chshu/openthread,srickardti/openthread,srickardti/openthread,xiaom-GitHub/openthread,LeZhang2016/openthread,lanyuwen/openthread,erja-gp/openthread,xiaom-GitHub/openthread,gandreello/openthread,pvanhorn/openthread,lanyuwen/openthread,gandreello/openthread,georgecpr/openthread,georgecpr/openthread,LeZhang2016/openthread,librasungirl/openthread,chshu/openthread,lanyuwen/openthread,chshu/openthread,LeZhang2016/openthread,erja-gp/openthread,abtink/openthread,bukepo/openthread,xiaom-GitHub/openthread,pvanhorn/openthread,LeZhang2016/openthread,chshu/openthread,openthread/openthread,xiaom-GitHub/openthread,turon/openthread,abtink/openthread