Implement bitmap-granular (4k) metadata & data checksums

tests/test_vm_cont.sh

@@ -8,7 +8,8 @@ etcdctl --endpoints=http://127.0.0.1:12379/v3 del --prefix /vitastor/pg/state
 etcdctl --endpoints=http://127.0.0.1:12379/v3 del --prefix /vitastor/osd/state
 
 OSD_COUNT=3
-OSD_ARGS=
+OSD_ARGS="$OSD_ARGS"
+OFFSET_ARGS="$OFFSET_ARGS"
 for i in $(seq 1 $OSD_COUNT); do
     build/src/vitastor-osd --osd_num $i --bind_address 127.0.0.1 $OSD_ARGS --etcd_address $ETCD_URL $(build/src/vitastor-disk simple-offsets --format options ./testdata/test_osd$i.bin 2>/dev/null) >>./testdata/osd$i.log 2>&1 &
     eval OSD${i}_PID=$!