BUG #15688: psql cannot connect to database which uses TLS nginx reverse proxy with SSL client auth

The following bug has been logged on the website:

Bug reference:      15688
Logged by:          Magnus
Email address:      jahnen@in.tum.de
PostgreSQL version: 11.1
Operating system:   ArchLinux
Description:

```
psql "port=9876 host=****.me user=docker
sslcert=/home/magnus/mep/ca_mqtt/db.crt
sslkey=/home/magnus/mep/ca_mqtt/db_nopasswd.key
sslrootcert=/home/magnus/mep/ca_mqtt/ca.crt sslmode=require"
psql: server closed the connection unexpectedly
    This probably means the server terminated abnormally
    before or while processing the request.
```

nginx logs:
```

2019/03/12 15:35:59 [info] 6#6: *359 SSL_do_handshake() failed (SSL:
error:1408F10B:SSL routines:ssl3_get_record:wrong version number) while SSL
handshaking, client: 84.138.94.156, server: 0.0.0.0:9876,
2019/03/12 15:40:22 [info] 6#6: *488 SSL_do_handshake() failed (SSL:
error:1408F10B:SSL routines:ssl3_get_record:wrong version number) while SSL
handshaking, client: 84.138.94.156, server: 0.0.0.0:9876,
2019/03/12 15:40:16 [info] 6#6: *485 SSL_do_handshake() failed (SSL:
error:1408F10B:SSL routines:ssl3_get_record:wrong version number) while SSL
handshaking, client: 84.138.94.156, server: 0.0.0.0:9876,
2019/03/12 15:36:41 [info] 6#6: *411 SSL_do_handshake() failed (SSL:
error:1408F10B:SSL routines:ssl3_get_record:wrong version number) while SSL
handshaking, client: 84.138.94.156, server: 0.0.0.0:9876
```

See also here: 
https://youtrack.jetbrains.com/issue/DBE-7814