fd_hbs: change monitoring processes to use pdb and ref counting
fd_hbs: change monitoring processes to use pdb and ref counting

previously, a list of monitor references was used and multiple monitors may have been started
caijieming-baidu/scalaris,jvf/scalaris,caijieming-baidu/scalaris,scalaris-team/scalaris,scalaris-team/scalaris,scalaris-team/scalaris,scalaris-team/scalaris,jvf/scalaris,jvf/scalaris,caijieming-baidu/scalaris,jvf/scalaris,jvf/scalaris,scalaris-team/scalaris,scalaris-team/scalaris,jvf/scalaris,caijieming-baidu/scalaris,scalaris-team/scalaris,caijieming-baidu/scalaris,caijieming-baidu/scalaris,caijieming-baidu/scalaris,scalaris-team/scalaris,jvf/scalaris