Revert "app,command: disallow abbrev by default"

This reverts commit 1e3ef64179.

This changed a default behaviour and broke tempest (and possibly more)
when version 1.16.0 was released.

A proper implementation that allows abbrev to be disabled without
changing the default will follow.

Related-Bug: 1543841
Change-Id: Ib38617ad08d930df1dcf263f4812b746b858a245

cliff/app.py

@@ -122,7 +122,6 @@ class App(object):
         parser = argparse.ArgumentParser(
             description=description,
             add_help=False,
-            allow_abbrev=False,
             **argparse_kwargs
         )
         parser.add_argument(

cliff/command.py

@@ -34,7 +34,6 @@ class Command(object):
         parser = argparse.ArgumentParser(
             description=self.get_description(),
             prog=prog_name,
-            allow_abbrev=False,
         )
         return parser
 

cliff/tests/test_app.py

@@ -264,7 +264,8 @@ def test_option_parser_abbrev_issue():
         def build_option_parser(self, description, version):
             parser = super(MyApp, self).build_option_parser(
                 description,
-                version)
+                version,
+                argparse_kwargs={'allow_abbrev': False})
             parser.add_argument('--endpoint')
             return parser