patch 9.0.0336: tests are flaky because of using a common file name

Problem:    Tests are flaky because of using a common file name.
Solution:   Rename files and directories to be more unique.
diff --git a/src/testdir/dumps/Test_diff_06.0.dump b/src/testdir/dumps/Test_diff_06.0.dump
index 2032fba..458295b 100644
--- a/src/testdir/dumps/Test_diff_06.0.dump
+++ b/src/testdir/dumps/Test_diff_06.0.dump
@@ -16,5 +16,5 @@
 |~| @35||+1#0000000&|~+0#4040ff13&| @35
 |~| @35||+1#0000000&|~+0#4040ff13&| @35
 |~| @35||+1#0000000&|~+0#4040ff13&| @35
-|X+3#0000000&|f|i|l|e|1| @12|1|,|1| @11|A|l@1| |X+1&&|f|i|l|e|2| @12|1|,|1| @11|A|l@1
+|X+3#0000000&|d|i|f|i|l|e|1| @10|1|,|1| @11|A|l@1| |X+1&&|d|i|f|i|l|e|2| @10|1|,|1| @11|A|l@1
 |:+0&&|s|e|t| |d|i|f@1|o|p|t|+|=|c|o|n|t|e|x|t|:|0| @51