Make network connectivity nonblocking for boot.

This brings auto to VIRTUAL_DEVICE_BOOT_COMPLETED even with both RIL and
wifi missing. VIRTUAL_DEVICE_MOBILE_NETWORK_CONNECTED comes up when the
mobile network is present. On auto, the mobile network connected message
still only comes up after the setup flow is completed.

Bug: 110720387
Test: Ran cuttlefish auto target locally.
Change-Id: I8bcee212f68db809fcffbba2ac16dd4628edf3ca