[sonic-package-manager] do not modify config_db.json

[stepanblyschak]

What I did

Installing an app.ext currently inserts app.ext specific init config into redis CONFIG_DB, /etc/sonic/config_db.json and /etc/sonic/init_cfg.json.

Since on configuration reload and boot the configuration file is merged with /etc/sonic/init_cfg.json there is no point in modifying config_db.json.

This can cause issues when config_db.json is not up-to-date. This is not a problem to configuration reload due to config migration, but it is not a valid JSON according to YANG model which does not validate old schema.

How I did it

Removed the relevant part of the code.

How to verify it

Verified by ONIE installing SONiC and installing an extension. Previosuly it failed and complaining about config_db.json not being valid:

Leafref "../../LOOPBACK_INTERFACE_LIST/name" of value "Loopback0" points to a non-existing leaf.

This is due to missing "Loopback0": {} in the LOOPBACK_INTERFACE table. This is not a problem since db_migrator can deal with it.

With this change, this is fixed - config_db.json is not modified, however app.ext initial configuration is inserted into redis CONFIG_DB after configuration reload or reboot.

Previous command output (if the output of a command-line utility has changed)

New command output (if the output of a command-line utility has changed)