bindings: allow users to switch between virtualization and non-virtualization mode

bindings: allow users to switch between virtualization and non-virtualization mode

When LXCFS has a bug and provides wrong or inconsistent values user
often want to turn off virtualization until we have figured out a fix
and rollout an upgrade to reload the shared library. Allow them to
toggle between virtualization mode and non-virtualization mode by
sending SIGUSR2 to lxcfs:

 Kernel supports pidfds
 api_extensions:
 - cgroups
 - sys_cpu_online
 - proc_cpuinfo
 - proc_diskstats
 - proc_loadavg
 - proc_meminfo
 - proc_stat
 - proc_swaps
 - proc_uptime
 - shared_pidns
 - cpuview_daemon
 - loadavg_daemon
 - pidfds
 Switched into non-virtualization mode
 Switched into virtualization mode
 Switched into non-virtualization mode
 Switched into virtualization mode
 Switched into non-virtualization mode

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>