git p4 test: cleanup_git should make a new $git

For convenience, leave one in place at the end of each
test so that it is not necessary to build a new one.  This
makes it consistent with $cli.

Signed-off-by: Pete Wyckoff <pw@padd.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/lib-git-p4.sh

@@ -99,5 +99,6 @@ kill_p4d() {
 }
 
 cleanup_git() {
-	rm -rf "$git"
+	rm -rf "$git" &&
+	mkdir "$git"
 }