Make logged_in more accurate

I found this while writing integration tests. If you try to login
with an incorrect username and password, mwclient correctly raises
mwclient.errors.LoginError...but if you then check logged_in, it
is True. Clearly that's wrong.

The logic for setting logged_in will basically consider us logged
in any time we process an API call and there is no 'anon' key in
the userinfo dict *or there is no userinfo dict at all*. The last
API call processed on a failed login attempt has no userinfo
dict.

This tweaks it so we only changed the logged_in value (in either
direction) if the API call we're handling has a userinfo dict.

We also fix the type of the empty userinfo we create if there
isn't one in the call (no idea why it was a tuple, it doesn't
really matter but it's weird) and explicitly set self.logged_in
to False in Site initialization. I don't think this is strictly
necessary as we can expect the init process to result in at least
one API call with a userinfo dict, but it feels more correct.

Signed-off-by: Adam Williamson <awilliam@redhat.com>

mwclient/client.py

@@ -102,6 +102,7 @@ class Site:
         self.compress = compress
         self.max_lag = str(max_lag)
         self.force_login = force_login
+        self.logged_in = False
         if reqs and connection_options:
             raise ValueError(
                 "reqs is a deprecated alias of connection_options. Do not specify both."
@@ -381,13 +382,14 @@ class Site:
         try:
             userinfo = info['query']['userinfo']
         except KeyError:
-            userinfo = ()
+            userinfo = {}
         if 'blockedby' in userinfo:
             self.blocked = (userinfo['blockedby'], userinfo.get('blockreason', ''))
         else:
             self.blocked = False
         self.hasmsg = 'messages' in userinfo
-        self.logged_in = 'anon' not in userinfo
+        if userinfo:
+            self.logged_in = 'anon' not in userinfo
         if 'warnings' in info:
             for module, warning in info['warnings'].items():
                 if '*' in warning: