remove global SIGCHILD handler to avoid conflicts
remove global SIGCHILD handler to avoid conflicts

Executing Qemu via cmd.Run() installs it's own SIG handler
to wait until Qemu has become a daemon.
Under certain conditions the global SIGCHILD handler in containerd.go
catches the SIGCHILD from the qemu process and the process is gone.
Later on in /usr/local/go/src/os/wait_waitid.go
the syscall SYS_WAITID triggerd by cmd.Run() also starts waiting for the
process to become waitable but panics with 'waitid: no child processes'.
This patch removes the global SIGCHILD handler.

Signed-off-by: Peter Morjan <964d0cf54dbf76d367f54f543a3db8d083ad8566@de.ibm.com>

gao-feng/runv,gao-feng/runv,jinfenw/runv,hyperhq/runv,bergwolf/runv,hyperhq/runv,jinfenw/runv,laijs/runv,feiskyer/runv,feiskyer/runv,bergwolf/runv,jinfenw/runv,gnawux/runv,laijs/runv,bergwolf/runv,gnawux/runv,laijs/runv,hyperhq/runv,gao-feng/runv,gnawux/runv