Add opportunity to directly update headers

Added change in request's methods in rest_client
for directly updating headers.
If someone want to add some custom headers to default headers
he can pass variable extra_headers=True in one of
the request's methods(POST/PUT/...) and headers should be
added to default headers

Change-Id: Ifbe49a9f7a6e2de780953ef9dcd39e443d74d151
Closes-bug: 1295661
diff --git a/tempest/services/object_storage/object_client.py b/tempest/services/object_storage/object_client.py
index 49f7f49..c4f5f4c 100644
--- a/tempest/services/object_storage/object_client.py
+++ b/tempest/services/object_storage/object_client.py
@@ -146,13 +146,19 @@
         self.service = CONF.object_storage.catalog_type
         self.format = 'json'
 
-    def request(self, method, url, headers=None, body=None):
+    def request(self, method, url, extra_headers=False, headers=None,
+                body=None):
         """A simple HTTP request interface."""
         dscv = CONF.identity.disable_ssl_certificate_validation
         self.http_obj = http.ClosingHttp(
             disable_ssl_certificate_validation=dscv)
         if headers is None:
             headers = {}
+        elif extra_headers:
+            try:
+                headers.update(self.get_headers())
+            except (ValueError, TypeError):
+                headers = {}
 
         # Authorize the request
         req_url, req_headers, req_body = self.auth_provider.auth_request(