Hyper-V: Remove useless use of "else" clause on for loop

"else" on for loops is only important if the loop contains a "break"
statement.  Without a "break", the else block is _always_ executed and
it is clearer just to omit "else".

This change also enables the corresponding pylint warning, now that the
only offending case has been fixed.

Change-Id: Ibe8761cb40a7d2d564aa718d62c9f383b5ad711e

.pylintrc

@@ -68,7 +68,6 @@ disable=
  unused-argument,
  unused-import,
  unused-variable,
- useless-else-on-loop,
 # "C" Coding convention violations
  bad-continuation,
  invalid-name,

neutron/plugins/ml2/drivers/mech_hyperv.py

@@ -51,7 +51,4 @@ class HypervMechanismDriver(mech_agent.SimpleAgentMechanismDriverBase):
             for pattern in mappings:
                 if re.match(pattern, segment[api.PHYSICAL_NETWORK]):
                     return True
-            else:
-                return False
-        else:
-            return False
+        return False