More specific path checks (file vs directory).

gns3server/server.py

@@ -77,7 +77,7 @@ class Server(object):
         self._projects_dir = os.path.expandvars(os.path.expanduser(server_config.get("projects_directory", "~/Documents/GNS3/projects")))
         self._temp_dir = server_config.get("temporary_directory", tempfile.gettempdir())
 
-        if not os.path.exists(self._projects_dir):
+        if not os.path.isdir(self._projects_dir):
             try:
                 os.makedirs(self._projects_dir)
                 log.info("projects directory '{}' created".format(self._projects_dir))