[fix] Openstack exporter update

This ps updates the logic to clear the token when it
receives authorization error from keystone.
This is a special case of 401.
When the exporter receives a 401 error from the keystone and the
application is not placement, we reset the token value such that on the
next retry it reinitialize the parameters.

Change-Id: I0c4bcb17aa420e31591405b6000a2db2821e2428

prometheus-openstack-exporter/exporter/check_os_api.py

@@ -96,6 +96,10 @@ class CheckOSApi(OSBase):
                         name, status_code, check['expect'])
                 )
                 status = self.FAIL
+                if status_code == 401 and name != 'placement':
+                    self.osclient.clear_token()
+                    logger.info(
+                        "Received 401 authorization error. Resetting the token.")
             else:
                 status = self.OK