Certificates implementation in "SSL forward proxy client and server authentication" scenario.

You are specifying forward proxy in your client SSL profile. For reverse proxy, it should look something like this:

ltm profile client-ssl CSSL-TESTVERINT {
    app-service none
    cert TESTVERINT.EXT.VIDEOTRON.COM.crt
    chain none
    defaults-from clientssl
    key TESTVERINT.EXT.VIDEOTRON.COM.key
    }