Revert "vnode: disable buffer pool recycling for 3.0 merging"

This reverts commit ba68d5d7.

source/dnode/vnode/src/vnd/vnodeCommit.c

@@ -75,10 +75,10 @@ static int32_t vnodeGetBufPoolToUse(SVnode *pVnode) {
       break;
     } else {
       vDebug("vgId:%d no free buffer pool on %d try, try to recycle...", TD_VID(pVnode), nTry);
-      /*
+
       code = vnodeTryRecycleBufPool(pVnode);
       TSDB_CHECK_CODE(code, lino, _exit);
-      */
+
       if (pVnode->freeList == NULL) {
         vDebug("vgId:%d no free buffer pool on %d try, wait %d ms...", TD_VID(pVnode), nTry, WAIT_TIME_MILI_SEC);