tap-test: clean up temporary test directories as intended

The script created ./.testtmp but looked for ./.test, which isn't
going to work.

This means the various "ostree trivial-httpd --autoexit" processes
actually exit, because their web roots are cleaned up now.

Signed-off-by: Simon McVittie <smcv@debian.org>

Closes: #232
Approved by: cgwalters

buildutil/tap-test

@@ -13,7 +13,7 @@ touch ${tempdir}/.testtmp
 function cleanup () {
     if test -n "${TEST_SKIP_CLEANUP:-}"; then
 	echo "Skipping cleanup of ${tempdir}"
-    else if test -f ${tempdir}/.test; then
+    else if test -f ${tempdir}/.testtmp; then
 	rm "${tempdir}" -rf
     fi
     fi