iotests: Use _rm_test_img for deleting test images

Just rm will not delete external data files.  Use _rm_test_img every
time we delete a test image.

(In the process, clean up the indentation of every _cleanup() this patch
touches.)

((Also, use quotes consistently.  I am happy to see unquoted instances
like "rm -rf $TEST_DIR/..." go.))

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-id: 20191107163708.833192-16-mreitz@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
diff --git a/tests/qemu-iotests/153 b/tests/qemu-iotests/153
index e590902..2b13111 100755
--- a/tests/qemu-iotests/153
+++ b/tests/qemu-iotests/153
@@ -30,13 +30,9 @@
 _cleanup()
 {
     _cleanup_test_img
-    rm -f "${TEST_IMG}.base"
-    rm -f "${TEST_IMG}.overlay"
-    rm -f "${TEST_IMG}.convert"
-    rm -f "${TEST_IMG}.a"
-    rm -f "${TEST_IMG}.b"
-    rm -f "${TEST_IMG}.c"
-    rm -f "${TEST_IMG}.lnk"
+    for img in "${TEST_IMG}".{base,overlay,convert,a,b,c,lnk}; do
+        _rm_test_img "$img"
+    done
 }
 trap "_cleanup; exit \$status" 0 1 2 3 15