What's the best way to fix this Drush clear cache bug?
I'm going to add an answer (don't want to bury this in the comments) that for a 4.7.17 - with two separate databases - drupal and civicrm; this is NOT an issue; 

My view with custom data before and after and in-between:

[karin@louise bin]$ sudo -u apache drush civicrm-upgrade-db
Starting with v4.7.16 -&gt; v4.7.17 upgrade ..                                                                                                      


Specifically trying to just drush cc all:

[karin@louise bin]$ sudo -u apache drush cc all


is fine - the way they were on 4.7.16 - with CiviCRM Custom field listed under Fields