Force an fsck.ufs after localization of a FreeBSD filesystem.

Apparently there are some issues with UFS2 support in Linux.
Fsck mostly fixes incorrect block counts:
    INCORRECT BLOCK COUNT I=1043374 (0 should be 8)
for inodes that get created by Linux (e.g., /etc/ssh host keys,
/var/emulab/boot stuff). Everything seems to be fine after the fsck.

Also: specify "-Zy" when creating LVMs so that old GPTs, superblocks, etc.
don't leak through. LVM seems to be frightfully deterministic in its
allocation strategies to the extent that virtual disks created in previous
experiments have their metadata show up in newer experiment LVMs.
All the things that are changed

clientside/tmcc/linux/xen/libvnode_xen.pm

@@ -2161,6 +2161,12 @@ sub vnodePreConfig($$$$$){
     }
   done:
     mysystem("umount $dev");
+
+    # XXX tmp
+    if ($vninfo->{'os'} eq "FreeBSD" && -x "$FSCKUFS") {
+	mysystem2("$FSCKUFS -yf $dev");
+    }
+
     # XXX let vnodesetup exit early
     if ($vsrelease eq "early" && $retval == 0) {
 	TBDebugTimeStamp("vnodePreConfig: touching $VMS/$vnode_id/running");
@@ -5294,7 +5300,7 @@ sub createThinPool($)
     }
 
     # Try to make it
-    if (mysystem2("lvcreate -i$num -L ${poolsize}g ".
+    if (mysystem2("lvcreate -Zy -i$num -L ${poolsize}g ".
 		  "--type thin-pool --thinpool $POOL_NAME $VGNAME")) {
 	print STDERR "createThinPool: could not create ${poolsize}g ".
 	    "thin pool\n";
@@ -5372,7 +5378,7 @@ again:
 	$flag = ALLOC_NOPOOL();
     }
     if ($flag == ALLOC_NOPOOL() || $flag == ALLOC_PREFERNOPOOL) {
-	if (!mysystem2("lvcreate -L $size -n $name -i${STRIPE_COUNT} ".
+	if (!mysystem2("lvcreate -Zy -L $size -n $name -i${STRIPE_COUNT} ".
 		       "$VGNAME")) {
 	    return 0;
 	}