Use -h, --help to show help messages.

Fixes bug 1023260
"quantumv2" command used '-H' and '--Help' to show help messages,
but it is inconsistent to the convention of option names used in
other OpenStack client lib commands. This commit fixes it.

Change-Id: I85c1e79c2cd08bcc0112ed2f10ca8210e9384687

quantumclient/shell.py

@@ -186,7 +186,7 @@ def build_option_parser(self, description, version):
             const=0,
             help='suppress output except warnings and errors', )
         parser.add_argument(
-            '-H', '--Help',
+            '-h', '--help',
             action=HelpAction,
             nargs=0,
             default=self,  # tricky