elbe-init: export http_proxy

it is used by virtapt to download the kinitrd/elbe-bootstrap pkg

Signed-off-by: Manuel Traut <manut@linutronix.de>
pkgutils: copy_kinitrd - except SystemError

it occurs if a configured proxy is not reachable or the internet connection
isn't working

Signed-off-by: Manuel Traut <manut@linutronix.de>