fix retrievel of group members and cache group members
fix retrievel of group members and cache group members

cernbox/core,owncloud/core,xx621998xx/server,xx621998xx/server,pixelipo/server,xx621998xx/server,sharidas/core,pollopolea/core,andreas-p/nextcloud-server,pmattern/server,nextcloud/server,lrytz/core,michaelletzgus/nextcloud-server,whitekiba/server,IljaN/core,lrytz/core,jbicha/server,Ardinis/server,andreas-p/nextcloud-server,pmattern/server,IljaN/core,andreas-p/nextcloud-server,nextcloud/server,endsguy/server,endsguy/server,pixelipo/server,pmattern/server,sharidas/core,IljaN/core,jbicha/server,endsguy/server,lrytz/core,pixelipo/server,Ardinis/server,whitekiba/server,pollopolea/core,sharidas/core,sharidas/core,phil-davis/core,andreas-p/nextcloud-server,owncloud/core,xx621998xx/server,nextcloud/server,pixelipo/server,bluelml/core,nextcloud/server,Ardinis/server,endsguy/server,jbicha/server,Ardinis/server,pollopolea/core,Ardinis/server,michaelletzgus/nextcloud-server,bluelml/core,pmattern/server,whitekiba/server,cernbox/core,whitekiba/server,cernbox/core,lrytz/core,pmattern/server,endsguy/server,andreas-p/nextcloud-server,bluelml/core,IljaN/core,cernbox/core,owncloud/core,pixelipo/server,xx621998xx/server,IljaN/core,pollopolea/core,michaelletzgus/nextcloud-server,pollopolea/core,jbicha/server,whitekiba/server,michaelletzgus/nextcloud-server,owncloud/core,lrytz/core,owncloud/core,cernbox/core,bluelml/core,sharidas/core,bluelml/core,jbicha/server