Reg removal of un-used Set Password D-Bus method API

[Thomaiyar, Richard Marian]

All,

As part of clean-up, planning to remove unused SetPassword D-Bus method 
API exposed through password.interface.yaml. OpenBMC master code doesn't 
rely on this API anymore, and uses pam_chauthtok() API to update the 
password (for security purposes). Even phosphor-user-manager don't 
expose SetPassword D-Bus method API. Following 2 commits are in review 
which will remove the same permanently.

Please let us know, if you have any concerns or require any further 
clarifications.

1. 
https://gerrit.openbmc-project.xyz/#/c/openbmc/phosphor-user-manager/+/18940/

2. 
https://gerrit.openbmc-project.xyz/#/c/openbmc/phosphor-dbus-interfaces/+/18943/

Regards,

Richard