lxc_init: s/SYSDEBUG()/SYSERROR()/g in remove_self
lxc_init: s/SYSDEBUG()/SYSERROR()/g in remove_self

Since we switched to execveat() whenever possible in
commit 4b5b3a2a299b ("execute: use execveat() syscall if supported")
it is unlikely that remove_self() has any job to do at all. So dumb down the
error levels.

Closes #2536.

Signed-off-by: Christian Brauner <48455ab3070520a2d174545c7239d6d0fabd9a83@ubuntu.com>

hallyn/lxc,hallyn/lxc,ss1h2a3tw/lxc,caglar10ur/lxc,ss1h2a3tw/lxc,ss1h2a3tw/lxc,hallyn/lxc,caglar10ur/lxc,caglar10ur/lxc