OSv hangs silently if no DHCP server

[nyh]

loader.cc calls dhcp_start(true). This "true" causes the initialization to wait until DHCP succeeds. If DHCP does not succeed, OSv will hang forever, silently because dhcp.cc uses dhcp_i which doesn't show anything (unless the -V option is used for verbose output). In this case the user is clueless why OSv is hanging. This can happen for example when the "-n" option is used (for using tap) but there is no DHCP server running (e.g., libvirt is not running).

We need be verbose (regardless of the -V option) when DHCP is not successful after a reasonable amount of time. It would also be nice for OSv to come up without networking in that case, instead of hanging forever.

[e74b254a966b1c]

How about, we modify dhcp_start, to take the number of attempts as an argument?
We could use a signed int, and represent an infinite number of attempts as a negative value.

[indykish]

+1, Troubleshooting guide helped => https://github.com/cloudius-systems/osv/wiki/Troubleshooting