Fix H404/405 violations for api tests(1/3)

There is a lot of H404/405 violations in Tempest now, and that leads
difficult to migrate the code to tempest-lib or the other projects'
repos. This patch fixes these violations for api tests except compute
and network.

Change-Id: I783862867732b76d836153bf9ef18fb4a5ec6c6e
diff --git a/tempest/api/object_storage/base.py b/tempest/api/object_storage/base.py
index 41a7d65..2621581 100644
--- a/tempest/api/object_storage/base.py
+++ b/tempest/api/object_storage/base.py
@@ -90,10 +90,8 @@
                 pass
 
     def assertHeaders(self, resp, target, method):
-        """
-        Common method to check the existence and the format of common response
-        headers
-        """
+        """Check the existence and the format of response headers"""
+
         self.assertThat(resp, custom_matchers.ExistsAllResponseHeaders(
                         target, method))
         self.assertThat(resp, custom_matchers.AreAllWellFormatted())