Cellular USB tethering improvements

What's Changed

• RDKBACCL-537: USB Dongle(RNDIS/MODEM type) support to CellularManager by @manigandanj in #8
• RDKBACCL-1275: wwan0 IP is not available in LTE (cellular) mode by @manigandanj in #9
• RDKBACCL-1239: Intermittently(> 50 % of times), Network unreachable o… by @manigandanj in #10

New Contributors

• @manigandanj made their first contribution in #8

Full Changelog: 1.0.0...1.0.1