do not use keys() method when iterating through dictionaries

pylint-1.6.4-1.fc26.noarch reports "C0201(consider-iterating-dictionary)" when
building FreeIPA, we have to fix these errors

https://fedorahosted.org/freeipa/ticket/6391

Reviewed-By: Martin Basti <mbasti@redhat.com>

ipapython/sysrestore.py

@@ -346,7 +346,7 @@ class StateFile(object):
         """
         root_logger.debug("Saving StateFile to '%s'", self._path)
 
-        for module in list(self.modules.keys()):
+        for module in list(self.modules):
             if len(self.modules[module]) == 0:
                 del self.modules[module]
 
@@ -359,7 +359,7 @@ class StateFile(object):
         p = SafeConfigParser()
         p.optionxform = str
 
-        for module in self.modules.keys():
+        for module in self.modules:
             p.add_section(module)
             for (key, value) in self.modules[module].items():
                 p.set(module, key, str(value))