Support for One-Arm Mode

By default, SonicOS assumes at least two interfaces, x0 for LAN and x1 for WAN in deployment. This might be true for hardware platforms. It is not the case any more for cloud platforms. SonicWall NSv instances on VMware ESXi support One-arm mode. One-arm mode allows NSv to also work when only one interface is present in the system. When there is one interface in NSv, by default, this is X0 on LAN, one-arm mode allows all traffic to come/go from X0.