Add support for client failover to the ipa command-line.

This adds a new global option to the ipa command, -f/--no-fallback. If this
is included then just the server configured in /etc/ipa/default.conf is used.
Otherwise that is tried first then all servers in DNS with the ldap SRV record
are tried.

Create a new Local() Command class for local-only commands. The help
command is one of these. It shouldn't need a remote connection to execute.

ticket #15

tests/test_xmlrpc/xmlrpc_test.py

@@ -42,7 +42,7 @@ fuzzy_uuid = Fuzzy(
 
 try:
     if not api.Backend.xmlclient.isconnected():
-        api.Backend.xmlclient.connect()
+        api.Backend.xmlclient.connect(fallback=False)
     res = api.Command['user_show'](u'notfound')
 except errors.NetworkError:
     server_available = False
@@ -103,7 +103,7 @@ class XMLRPC_test(object):
                 'Server not available: %r' % api.env.xmlrpc_uri
             )
         if not api.Backend.xmlclient.isconnected():
-            api.Backend.xmlclient.connect()
+            api.Backend.xmlclient.connect(fallback=False)
 
     def tearDown(self):
         """