Currently CRIU traces syscalls to catch a moment, when sigreturn() is
called. Now we trace recv(cmd), close(logfd), close(cmdfd), sigreturn().

We can reduce a number of steps by using hw breakpoints. A breakpoint is
set before sigreturn, so we will need to trace only it.
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>