osxkeychain: erase all matching credentials

Other credential managers erased all matching credentials, as indicated
by a test case that osxkeychain failed:

    15 - helper (osxkeychain) erases all matching credentials

Signed-off-by: Bo Anderson <mail@boanderson.me>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/credential/osxkeychain/git-credential-osxkeychain.c

@@ -182,7 +182,8 @@ static OSStatus delete_internet_password(void)
 	if (!protocol || !host)
 		return -1;
 
-	attrs = CREATE_SEC_ATTRIBUTES(NULL);
+	attrs = CREATE_SEC_ATTRIBUTES(kSecMatchLimit, kSecMatchLimitAll,
+				      NULL);
 	result = SecItemDelete(attrs);
 	CFRelease(attrs);