[image]: expand dockerfs.tar.gz directly on to disk without intermedi…

…ate file (#715)

installer/x86_64/install.sh

@@ -422,12 +422,11 @@ else
 fi
 
 # Decompress the file for the file system directly to the partition
-unzip $ONIE_INSTALLER_PAYLOAD -d $demo_mnt/$image_dir
+unzip -o $ONIE_INSTALLER_PAYLOAD -x "$FILESYSTEM_DOCKERFS" -d $demo_mnt/$image_dir
 
-if [ -f $demo_mnt/$image_dir/$FILESYSTEM_DOCKERFS ]; then
-    TAR_EXTRA_OPTION="--numeric-owner"
-    cd $demo_mnt/$image_dir && mkdir -p $DOCKERFS_DIR && tar x $TAR_EXTRA_OPTION -f $FILESYSTEM_DOCKERFS -C $DOCKERFS_DIR && rm -f $FILESYSTEM_DOCKERFS; cd $OLDPWD
-fi
+TAR_EXTRA_OPTION="--numeric-owner"
+mkdir -p $demo_mnt/$image_dir/$DOCKERFS_DIR
+unzip -op $ONIE_INSTALLER_PAYLOAD "$FILESYSTEM_DOCKERFS" | tar xz $TAR_EXTRA_OPTION -f - -C $demo_mnt/$image_dir/$DOCKERFS_DIR
 
 # Create loop device for /var/log to limit its size to $VAR_LOG_SIZE MB
 if [ -f $demo_mnt/disk-img/var-log.ext4 ]; then