GetPath() test case for path `system` can fail if slice has the wrong order

This specific test case can fail if the returned slice ([]*gnmi.Update) is not in the right order as encountered here.

Description

Expected Behavior

This testcase should not have random behaviour

Actual Behavior

Has random behaviour

Possible Fix

Sort the slice before comparing.

Steps to Reproduce

Context

Your Environment

• Version used:
• Environment name and version (e.g. go v1.16.3 on FreeBSD 13.0-current):
• Server type and version:
• Operating System and version: