[mle] remove sleepy child in all roles (#4234)
[mle] remove sleepy child in all roles (#4234)

This commit fixes an issue that indirect messages for sleepy child are
not correctly cleared in some cases.

This issue can cause sleepy nodes unable to reattach for a long time,
or even forever.
srickardti/openthread,openthread/openthread,bukepo/openthread,lanyuwen/openthread,chshu/openthread,jwhui/openthread,librasungirl/openthread,srickardti/openthread,librasungirl/openthread,openthread/openthread,chshu/openthread,srickardti/openthread,chshu/openthread,chshu/openthread,jwhui/openthread,abtink/openthread,bukepo/openthread,librasungirl/openthread,bukepo/openthread,abtink/openthread,abtink/openthread,openthread/openthread,lanyuwen/openthread,jwhui/openthread,openthread/openthread,bukepo/openthread,lanyuwen/openthread,jwhui/openthread,abtink/openthread,chshu/openthread,lanyuwen/openthread,lanyuwen/openthread,srickardti/openthread,librasungirl/openthread,lanyuwen/openthread,chshu/openthread