Fix deleting reflog entries from HEAD reflog

dwim_ref() used to resolve HEAD symbolic ref to its target (i.e. current
branch).  This incorrectly removed the reflog entry from the current
branch when 'git reflog delete HEAD@{1}' was asked for.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t1410-reflog.sh

@@ -175,7 +175,7 @@ test_expect_success 'recover and check' '
 
 '
 
-test_expect_failure 'delete' '
+test_expect_success 'delete' '
 	echo 1 > C &&
 	test_tick &&
 	git commit -m rat C &&