util: buffer: Remove virBufferError

The function now does not return an error so we can drop it fully.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>

tests/testutils.c

@@ -763,8 +763,6 @@ virTestLogContentAndReset(void)
 {
     char *ret;
 
-    if (virBufferError(&testLog.buf))
-        return NULL;
     ret = virBufferContentAndReset(&testLog.buf);
     if (!ret)
         ret = g_strdup("");