Make navigation to definitions follow imports

This fixes microsoft#1638 and simplifies the code (to what I believe that
@davidhalter had in mind in
microsoft#1033 (comment)).

This change means that all of the test cases recently added to
'navigation.tests.ts' now pass, meaning that navigtion to the
definition of functions works through imports and goes to the
original function, even when that function is decorated.

pythonFiles/completion.py

@@ -570,21 +570,7 @@ def _process_request(self, request):
             sys_path=sys.path, environment=self.environment)
 
         if lookup == 'definitions':
-            defs = []
-            try:
-                defs = self._get_definitionsx(script.goto_definitions(follow_imports=False), request['id'])
-            except:
-                pass
-            try:
-                if len(defs) == 0:
-                    defs = self._get_definitionsx(script.goto_definitions(), request['id'])
-            except:
-                pass
-            try:
-                if len(defs) == 0:
-                    defs = self._get_definitionsx(script.goto_assignments(), request['id'])
-            except:
-                pass
+            defs = self._get_definitionsx(script.goto_assignments(follow_imports=True), request['id'])
             return json.dumps({'id': request['id'], 'results': defs})
         if lookup == 'tooltip':
             if jediPreview: