iotests: 020: Use TEST_IMG override instead of "mv"

Signed-off-by: NFam Zheng <famz@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Message-id: 1450752561-9300-4-git-send-email-famz@redhat.com
Signed-off-by: NMax Reitz <mreitz@redhat.com>

tests/qemu-iotests/020

@@ -56,6 +56,9 @@ fi
 
 TEST_OFFSETS="0 4294967296"
 
+TEST_IMG_SAVE="$TEST_IMG"
+TEST_IMG="$TEST_IMG.base"
+
 _make_test_img 6G
 
 echo "Filling base image"
@@ -73,7 +76,7 @@ _check_test_img
 echo "Creating test image with backing file"
 echo
 
-mv "$TEST_IMG" "$TEST_IMG.base"
+TEST_IMG="$TEST_IMG_SAVE"
 _make_test_img -b "$TEST_IMG.base" 6G
 
 echo "Filling test image"
@@ -89,7 +92,7 @@ done
 _check_test_img
 
 $QEMU_IMG commit "$TEST_IMG"
-mv "$TEST_IMG.base" "$TEST_IMG"
+TEST_IMG="$TEST_IMG.base"
 
 echo "Reading from the backing file"
 echo

tests/qemu-iotests/020.out

 QA output created by 020
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=6442450944
+Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=6442450944
 Filling base image
 
 === IO: pattern 0