tool: prepend output_dir in header callback

When Content-Disposition parsing is used and an output dir is prepended,
make sure to store that new file name correctly so that it can be used
for setting the file timestamp when --remote-time is used.

Extended test 3012 to verify.

Co-Authored-by: Jay Satiro
Reported-by: hgdagon on github
Fixes #12614
Closes #12617

tests/data/test3012

@@ -4,6 +4,7 @@
 -O
 -J
 --output-dir
+--remote-time
 </keywords>
 </info>
 #
@@ -36,10 +37,10 @@ http
 http
 </features>
 <name>
---output-dir with -J
+--output-dir with -J and -R
 </name>
 <command option="no-output,no-include">
-http://%HOSTIP:%HTTPPORT/this/is/the/%TESTNUMBER -OJ --output-dir %PWD/%LOGDIR
+http://%HOSTIP:%HTTPPORT/this/is/the/%TESTNUMBER -OJR --output-dir %PWD/%LOGDIR
 </command>
 </client>