docs: Fix incorrect docstrings in reStructuredText format

Several docstrings have incorrect format, what prevents to generate
a documentation using sphinx-apidoc extension.

Change-Id: I66431c7030089173d7635c1e2a72765db21f9780
diff --git a/HACKING.rst b/HACKING.rst
index e8791f8..eb6551a 100644
--- a/HACKING.rst
+++ b/HACKING.rst
@@ -6,7 +6,7 @@
 - Step 2: Read on
 
 Tempest Specific Commandments
-------------------------------
+-----------------------------
 
 - [T102] Cannot import OpenStack python clients in tempest/api &
   tempest/scenario tests