tests 1348 to 1363: test definition polishing

Verify that the "Saved to filename 'blabla'" message is only displayed when
the 'blabla' filename being used _actually_ has been specified by the server
in the Content-Disposition header.

Use relative path for unintended file creation postcheck.

tests/data/test1352

@@ -71,7 +71,6 @@ mooo
 150 Binary data connection for 1352 () (10 bytes).
 226 File transfer complete
 221 bye bye baby
-curl: Saved to filename '%PWD/log/file1352'
 </file2>
 <stripfile2>
 s/^(229 Entering Passive Mode \().*(\).*)/${1}stripped${2}/