Atomically apply new hostname.if(5)
Atomically apply new hostname.if(5)

This fixes an issue when the interface being configured is the
interface through which ssh traffic is forwarded.

In a complex scenario, one needs to disable the default interface for
NAT, and use other interface for ssh. In this case, when vagrant run
`ifconfig #{ifname} inet delete`, the second ifconfig that is supposed
to restore interface settings will never be called. This might be a rare
need, but it is also strongly recommended to use `netstart` when
reconfiguring interfaces after updating `hostname.if(5)`.

The issue can be triggered when ssh connection has issues between two
`ifconfig` commands.

bryson/vagrant,crashlytics/vagrant,bryson/vagrant,chrisroberts/vagrant,PatrickLang/vagrant,mitchellh/vagrant,chrisroberts/vagrant,marxarelli/vagrant,crashlytics/vagrant,crashlytics/vagrant,sni/vagrant,sni/vagrant,gitebra/vagrant,mitchellh/vagrant,sni/vagrant,marxarelli/vagrant,chrisroberts/vagrant,marxarelli/vagrant,gitebra/vagrant,PatrickLang/vagrant,gitebra/vagrant,crashlytics/vagrant,PatrickLang/vagrant,sni/vagrant,gitebra/vagrant,marxarelli/vagrant,bryson/vagrant,bryson/vagrant,mitchellh/vagrant,mitchellh/vagrant,chrisroberts/vagrant,PatrickLang/vagrant