Fix and prevent some segfaults in ab:

Fix and prevent some segfaults in ab:

* support/ab.c (main): Fail if given concurrency level greater than
number of requests, to prevent segfaults later.
(ssl_print_cert_info): Use the correct buffer size.
(ssl_start_connect): SSL_get_peer_cert_chain doesn't bump refcounts,
so don't free the cert chain here.
(test): Use both calloc parameters (unrelated cleanup).

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@161437 13f79535-47bb-0310-9956-ffa450edef68