Merge drop-xvfb-run [f=] [r=ericsnowcurrently,landscape-builder,free.ekanayaka] [a=Данило Шеган]
Drop xvfb-run from 'make check'

xvfb was probably used for our former GUI code, but now seems unnecessary.

I sneak in a LC_ALL=C there to make landscape.lib.tests.test_network.NetworkInfoTest.test_get_active_device_info pass if you've got Serbian local set up too.