Add boolean field for default_content_http_proxy in HTTProxy entity

Signed-off-by: Gaurav Talreja <gtalreja@redhat.com>

nailgun/entities.py

@@ -5421,6 +5421,7 @@ def __init__(self, server_config=None, **kwargs):
             'organization': entity_fields.OneToManyField(Organization),
             'location': entity_fields.OneToManyField(Location),
             'cacert': entity_fields.StringField(),
+            'default_content_http_proxy': entity_fields.BooleanField(),
         }
         self._meta = {'api_path': 'api/v2/http_proxies'}
         super().__init__(server_config=server_config, **kwargs)