Bug 1316994 - Modify tstclnt so that it has an auto-disconnect and

resume. r=mt

Summary:

It is difficult to resumption and 0-RTT with tstclnt as it currently is.
This CL fixes that. The changes involve two new flags:

A -- Read a fixed request from a file and use that instead of
     reading from stdin
L -- Disconnect and reconnect L - 1 times.

Reviewers: mt

Differential Revision: https://nss-review.dev.mozaws.net/D39

Fix npds