Fix spurious clock skew caused by preauth delay

Commit 37b0e55e21926c7875b7176e24e13005920915a6 (#7063) prevented
clock skew caused by preauth delay by recording the time of the
initial request.  However, it failed to take into account delay
between requests due to prompting during preauthentication.  Fix this
by recording the request time for each request.

ticket: 7656 (new)