Always set nodev,nosuid,noexec when mounting sysfs
Always set nodev,nosuid,noexec when mounting sysfs

This seems to help in certain edge cases inside LXC containers
and should not hurt otherwise.
Fixes #749

ultimate-pa/benchexec,ultimate-pa/benchexec,sosy-lab/benchexec,sosy-lab/benchexec,ultimate-pa/benchexec,ultimate-pa/benchexec,sosy-lab/benchexec,sosy-lab/benchexec,ultimate-pa/benchexec,ultimate-pa/benchexec,sosy-lab/benchexec,sosy-lab/benchexec