Fix/Set mandatory=false for optional response params

[ShobhitAd]

This PR is ready for review.

Risk

This PR makes minor API changes.

Testing Plan

ATF tests

Summary

This PR changes the mandatory attribute for parameters(other than success and resultCode) in RPC responses(in the MOBILE_API) from mandatory=true to mandatory=false.

Currently, core is only guaranteed to return resultCode and success for all RPC responses to mobile. In the case of an error, core may not return other parameters. If those other parameters have mandatory=true in the API spec that could cause issues on the mobile side.

CLA

• I have signed the CLA

[LuxoftAKutsan]

@ShobhitAd I would check SDL code for the usage of these variables.

In some places, the developer may try to get this variable from smart-object without checking if the appropriate key exists, because by API it should be mandatory.