refs: fix valgrind suppression file

Add all of the ways in which check_refname_format violates valgrind's
expectations to the valgrind suppression file; remove an assumption about
the call chain of check_refname_format from same.

Signed-off-by: David Turner <dturner@twitter.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/valgrind/default.supp

@@ -50,10 +50,17 @@
 	fun:copy_ref
 }
 {
-	ignore-sse-check_refname_format
+	ignore-sse-check_refname_format-addr
 	Memcheck:Addr8
 	fun:check_refname_format
-	fun:cmd_check_ref_format
-	fun:handle_builtin
-	fun:main
+}
+{
+	ignore-sse-check_refname_format-cond
+	Memcheck:Cond
+	fun:check_refname_format
+}
+{
+	ignore-sse-check_refname_format-value
+	Memcheck:Value8
+	fun:check_refname_format
 }