Add an error code for RoR failure due to no network

This gives us detailed information on whether server based RoR fails
due to no network after reboot. There might be a race condition
when the device gets network (check) after RoR fails in gmscore (use).
But the case should be rare, and it's acceptable for metrics purpose.

Also mock the methods to read timeouts. This helps avoids denail to read
device_config when running test on internal targets.

Bug: 179105110
Test: trigger a server based ror, check error code
Change-Id: If600e8e06d7707da7160fec66d71bc9341327965