[bugfix] NativeBroker#doCopyCollection should take READ_LOCK (not WRITE_LOCK) on source sub-collections
[bugfix] NativeBroker#doCopyCollection should take READ_LOCK (not WRITE_LOCK) on source sub-collections

Closes https://github.com/eXist-db/exist/issues/1289

joewiz/exist,wshager/exist,ambs/exist,eXist-db/exist,joewiz/exist,opax/exist,dizzzz/exist,ambs/exist,olvidalo/exist,RemiKoutcherawy/exist,wolfgangmm/exist,dizzzz/exist,joewiz/exist,olvidalo/exist,hungerburg/exist,wshager/exist,wolfgangmm/exist,windauer/exist,wolfgangmm/exist,olvidalo/exist,ljo/exist,ambs/exist,ljo/exist,hungerburg/exist,wolfgangmm/exist,eXist-db/exist,hungerburg/exist,RemiKoutcherawy/exist,wshager/exist,hungerburg/exist,dizzzz/exist,ljo/exist,RemiKoutcherawy/exist,dizzzz/exist,adamretter/exist,RemiKoutcherawy/exist,lcahlander/exist,adamretter/exist,wolfgangmm/exist,adamretter/exist,dizzzz/exist,windauer/exist,eXist-db/exist,joewiz/exist,windauer/exist,ambs/exist,opax/exist,windauer/exist,olvidalo/exist,opax/exist,opax/exist,ambs/exist,lcahlander/exist,RemiKoutcherawy/exist,wshager/exist,RemiKoutcherawy/exist,adamretter/exist,wolfgangmm/exist,adamretter/exist,windauer/exist,ljo/exist,adamretter/exist,lcahlander/exist,lcahlander/exist,wshager/exist,wshager/exist,lcahlander/exist,eXist-db/exist,lcahlander/exist,olvidalo/exist,windauer/exist,dizzzz/exist,ljo/exist,hungerburg/exist,joewiz/exist,ambs/exist,ljo/exist,eXist-db/exist,joewiz/exist,opax/exist,eXist-db/exist