Revert "guests/tinycore: error if DHCP [GH-4699]"

This reverts commit 64139f2158a957998126f6cf2abcf1042f982175.
Add support for DHCP on tinycore
Merge branch 'master' of github.com:tarrant/vagrant
Merge pull request #4710 from tarrant/master

guests/tinycore: Add DHCP support for tinycore