BUG/MEDIUM: ssl/crt-list: correctly insert crt-list line if crt already loaded

BUG/MEDIUM: ssl/crt-list: correctly insert crt-list line if crt already loaded

In issue #940, it was reported that the crt-list does not work correctly
anymore. Indeed when inserting a crt-list line which use a certificate
previously seen in the crt-list, this one won't be inserted in the SNI
list and will be silently ignored.

This bug was introduced by commit  47da821 "MEDIUM: ssl: emulates the
multi-cert bundles in the crtlist".

This patch also includes a reg-test which tests this issue.

This bugfix must be backported in 2.3.

(cherry picked from commit 50c03aac0417f7d70f98f31e513441c0fb743110)
Signed-off-by: William Lallemand <wlallemand@haproxy.org>