Replace 'dd' in tests with use of guestfish 'sparse' command.

'dd' is a very inefficient way to create files.  'truncate' is
better, but unfortunately that command is not available in RHEL 5.
So use the guestfish 'sparse' command instead (which also avoids
allocating disk space).
(cherry picked from commit 175c01d233)

regressions/rhbz503169c10.sh

@@ -22,9 +22,9 @@
 set -e
 
 rm -f test1.img
-dd if=/dev/zero of=test1.img bs=1024k count=10
 
-../fish/guestfish -a test1.img <<EOF
+../fish/guestfish <<EOF
+sparse test1.img 10M
 launch
 part-disk /dev/sda mbr
 mkfs ext2 /dev/sda1

regressions/rhbz503169c13.sh

@@ -27,9 +27,9 @@
 set -e
 
 rm -f test1.img
-dd if=/dev/zero of=test1.img bs=1024k count=10
 
-../fish/guestfish -a test1.img <<EOF
+../fish/guestfish <<EOF
+sparse test1.img 10M
 run
 part-disk /dev/sda mbr
 mkfs ext2 /dev/sda1

regressions/test-bootbootboot.sh

@@ -24,7 +24,6 @@
 set -e
 
 rm -f test1.img
-dd if=/dev/zero of=test1.img bs=1024k count=500
 
 n=10
 if [ -n "$1" ]; then n=$1; fi
@@ -33,7 +32,7 @@ export LIBGUESTFS_DEBUG=1
 
 for i in $(seq 1 $n); do
   echo Test boot $i of $n ...
-  ../fish/guestfish -a test1.img run
+  ../fish/guestfish sparse test1.img 500M : run
 done
 
 rm test1.img