Workaround for "configuration file test failed" under OpenVZ.

Workaround for "configuration file test failed" under OpenVZ.

If nginx was used under OpenVZ and a container with nginx was suspended
and resumed, configuration tests started to fail because of EADDRINUSE
returned from listen() instead of bind():

# nginx -t
nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: [emerg] listen() to 0.0.0.0:80, backlog 511 failed (98: Address already in use)
nginx: configuration file /etc/nginx/nginx.conf test failed

With this change EADDRINUSE errors returned by listen() are handled
similarly to errors returned by bind(), and configuration tests work
fine in the same environment:

# nginx -t
nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: configuration file /etc/nginx/nginx.conf test is successful

More details about OpenVZ suspend/resume bug:
https://bugzilla.openvz.org/show_bug.cgi?id=2470