tests: start to use 4k mkfs

While newer system can detect need for 4K mkfs, on older test machines
running test suite over 4k is reporting problems.
Some more generic solution is needed thought.

test/shell/thin-merge.sh

@@ -22,6 +22,7 @@ MKFS=mkfs.ext2
 which $MKFS  || skip
 which fsck || skip
 
+MKFS="$MKFS -b4096"
 #
 # Main
 #

test/shell/topology-support.sh

@@ -23,7 +23,7 @@ lvdev_() {
 
 test_snapshot_mount() {
     lvcreate -aey -L4M -n $lv1 $vg "$dev1"
-    mkfs.ext3 "$(lvdev_ $vg $lv1)"
+    mkfs.ext3 -b4096 "$(lvdev_ $vg $lv1)"
     mkdir test_mnt
     mount "$(lvdev_ $vg $lv1)" test_mnt
     lvcreate -L4M -n $lv2 -s $vg/$lv1