Merge pull request #232 from wazo-platform/WAZO-3552-remove-yealink-common-files

WAZO-3552: Remove common configuration files for Yealink

Why: when using a provisioning key, it is not possible to configure a common file with URLs in them. The file is common to all the devices and is generated at wazo-provd startup. This means that there is no provisioning key available.

Reviewed-by: Francois Blackburn