Cert processing invalid, module certificate should be updated when a policy table update occurs

[mrapitis]

Bug Report

With the implementation of the EXTERNAL_PROPRIETARY policy mode in release 4.3.0, SDL Core should update the module certificate in the local file system when a policy table update occurs. Currently SDL core is retrieving its certificate directly out of the policy table. This issue is closely related to #2190

Reproduction Steps

Clone any branch of sdl core with a release version of 4.3.0 or above. Take note of the certificate processing flow, core will directly processes its certificates from its policy table database.

Expected Behavior

SDL Core will update the local file system when a policy table update occurs with the certificate provided via the updated policy table exchange.

Observed Behavior

Invalid certificate processing flow, data is not sourced properly as it should be.

OS & Version Information

• OS/Version: Ubuntu 16.04
• SDL Core Version: Release 4.5.1
• Testing Against: Tested with WebHMI and app built with 4.5.0 Android Proxy release