[System-1] adding system-1 banner deviations.

[fmolinar]

Adding delimiter to the input for modt and login banner, skipping empty string banner via new deviation.

[OpenConfigBot]

Pull Request Functional Test Report for #4078 / 0ab446e77a756e4f02bc6e5f94e3e048ff899015

Virtual Devices

Device	Test	Test Documentation	Job	Raw Log
Arista cEOS		System-1.1: System banner test
Cisco 8000E		System-1.1: System banner test
Cisco XRd		System-1.1: System banner test
Juniper ncPTX		System-1.1: System banner test
Nokia SR Linux		System-1.1: System banner test
Openconfig Lemming		System-1.1: System banner test

Hardware Devices

Device	Test	Test Documentation	Raw Log
Arista 7808		System-1.1: System banner test
Cisco 8808		System-1.1: System banner test
Juniper PTX10008		System-1.1: System banner test
Nokia 7250 IXR-10e		System-1.1: System banner test

Help

[AmrNJ]

Closing this PR as all necessary changes have been implemented with #4142