Fix InvalidRequestError in auto_schedule_routers

This was discussed in review [1], and was deferred until the time was ripe
for the appropriate fix. As suggested and reported, auto_schedule_routers
is too affected by this error.

This patch takes care of the issue, in a similar way.

[1] - https://review.openstack.org/#/c/112740/

Related-bug: #1354072
Closes-bug: #1360104

Change-Id: Ie3cb0c31dfa571c694cd38e19f72ff8503815635
Merge "Fix InvalidRequestError in auto_schedule_routers"