Add a rule for blocking "-" from rand_name call

data_utils.rand_name() appends randam charactors with a hypen like:

 def rand_name(name=''):
     randbits = str(random.randint(1, 0x7fffffff))
     if name:
         return name + '-' + randbits

So it is not necessary to specify a hypen in caller side.
This patch adds a hacking rule for blocking "-" at the end of argument
of rand_name() calls.

Change-Id: I9b9f25dbe5a3ef5ac5900113bcc46e0d911becc9
diff --git a/HACKING.rst b/HACKING.rst
index 04b5eb6..c776c49 100644
--- a/HACKING.rst
+++ b/HACKING.rst
@@ -14,6 +14,7 @@
 - [T105] Tests cannot use setUpClass/tearDownClass
 - [T106] vim configuration should not be kept in source files.
 - [T107] Check that a service tag isn't in the module path
+- [T108] Check no hyphen at the end of rand_name() argument
 - [N322] Method's default argument shouldn't be mutable
 
 Test Data/Configuration