BUG/MEDIUM: ssl/cli: crash when crt inserted into a crt-list

BUG/MEDIUM: ssl/cli: crash when crt inserted into a crt-list

The crash occures when the same certificate which is used on both a
server line and a bind line is inserted in a crt-list over the CLI.

This is quite uncommon as using the same file for a client and a server
certificate does not make sense in a lot of environments.

This patch fixes the issue by skipping the insertion of the SNI when no
bind_conf is available in the ckch_inst.

Change the reg-test to reproduce this corner case.

Should fix issue #1748.

Must be backported as far as 2.2. (it was previously in ssl_sock.c)