obs: build_binpkg: no network during build

Simulate that we don't have network during package builds in gerrit
verifications, like it is the case when the packages will be built by
OBS.

I've also considered using network namespaces via "unshare -n" or
bubblewrap, but it wouldn't be possible to create a loopback device
inside the network namespace inside docker (maybe with --privileged, but
not worth it) and e.g. the osmo-mgw tests rely on lo.

Depends: osmo-epdg I2bb0b5f608cd5d9a24c2a367425c524447bd002c
Change-Id: I00282552e9988d66fdc269c6230f0e1432ace360
4 files changed