fix statistics not working with monitor processes (regression of r7096)
fix statistics not working with monitor processes (regression of r7096)

use monitor:get_rrds/2 instead of sending messages
-> this breaks statistics with monitor_perf which will be fixed in the next commit
scalaris-team/scalaris,jvf/scalaris,scalaris-team/scalaris,jvf/scalaris,caijieming-baidu/scalaris,caijieming-baidu/scalaris,scalaris-team/scalaris,caijieming-baidu/scalaris,caijieming-baidu/scalaris,caijieming-baidu/scalaris,scalaris-team/scalaris,jvf/scalaris,jvf/scalaris,jvf/scalaris,caijieming-baidu/scalaris,caijieming-baidu/scalaris,scalaris-team/scalaris,jvf/scalaris,scalaris-team/scalaris,scalaris-team/scalaris,jvf/scalaris,scalaris-team/scalaris