Rename the nginx ssl config file to match the final filename

This config file will ultimately exist as /etc/letsencrypt/options-ssl-nginx.conf
so we may as well use the right filename everywhere.

This is much easier to deal with in the Debian packaging.

MANIFEST.in

@@ -12,4 +12,4 @@ recursive-include letsencrypt_apache/tests/testdata *
 include letsencrypt_apache/options-ssl.conf
 
 recursive-include letsencrypt_nginx/tests/testdata *
-include letsencrypt_nginx/options-ssl.conf
+include letsencrypt_nginx/options-ssl-nginx.conf

letsencrypt_nginx/constants.py

@@ -11,6 +11,6 @@ CLI_DEFAULTS = dict(
 
 
 MOD_SSL_CONF = pkg_resources.resource_filename(
-    "letsencrypt_nginx", "options-ssl.conf")
+    "letsencrypt_nginx", "options-ssl-nginx.conf")
 """Path to the Nginx mod_ssl config file found in the Let's Encrypt
 distribution."""