gNOI support for system upgrade/reboot

The gRPC Network Operations Interface (gNOI) OS service remote procedure calls (RPCs) are updated to more efficiently manage software upgrades. These changes enable you to install software without immediate activation, validate the current configuration against any installed software version, and activate any installed software version.

The Install() RPC copies the software installation package to the device, validates the configuration against the specified software version, and installs the software. The Activate() RPC sets the specified software version as the next boot version. If the specified software version is already installed on the device, Install() instead validates the current configuration against the existing software image and stores the validated current configuration as the running configuration associated with that image. In previous releases, the Install() RPC only copies the software installation package to the device. The Activate() RPC performs the rest of the actions—validates the configuration, installs the software, and sets the software version as the next boot version.