Backport model.name from HEAD into 2.9

Gets this particular change from
55ea0e2 adds the name @Property into
a Model object. Couldn't directly cherry pick because of the other
stuff in the commit.

Author: cderici

juju/model.py

@@ -1021,6 +1021,14 @@ async def get_info(self):
 
         return self.info
 
+    @property
+    def name(self):
+        """Return the name of this model
+        """
+        if self._info is None:
+            raise JujuError("Model is not connected")
+        return self._info.name
+
     @property
     def info(self):
         """Return the cached client.ModelInfo object for this Model.