talloc: save errno over talloc_free

As we start to use errno more, it's a huge pain if talloc_free() can blatt
it (esp. destructors).

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>


(This used to be ctdb commit 76a0ca77feba14e1e1162c195ffbdf516e62aa4d)

ctdb/lib/talloc/talloc.c

@@ -746,7 +746,12 @@ void *talloc_named_const(const void *context, size_t size, const char *name)
 */
 int talloc_free(void *ptr)
 {
-	return _talloc_free(ptr);
+	int ret, saved_errno;
+
+	saved_errno = errno;
+	ret = _talloc_free(ptr);
+	errno = saved_errno;
+	return ret;
 }