Remove unused variables in the code

This commit removes unused variables or rename variables as "expected to
be unused" by using "_" prefix.

This covers only cases where fix was easy or only one unused variable
was in a module

Reviewed-By: Florence Blanc-Renaud <frenaud@redhat.com>
Reviewed-By: Stanislav Laznicka <slaznick@redhat.com>

ipapython/install/common.py

@@ -60,7 +60,7 @@ class Step(Installable):
         raise AttributeError('parent')
 
     def _install(self):
-        for nothing in self._installer(self.parent):
+        for _nothing in self._installer(self.parent):
             yield from_(super(Step, self)._install())
 
     @staticmethod
@@ -68,7 +68,7 @@ class Step(Installable):
         yield
 
     def _uninstall(self):
-        for nothing in self._uninstaller(self.parent):
+        for _nothing in self._uninstaller(self.parent):
             yield from_(super(Step, self)._uninstall())
 
     @staticmethod