crtools: fix backward compatibility

crtools should not failed, if new images are absent.
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

signalfd.c

@@ -129,6 +129,11 @@ static int collect_one_sigfd(void *o, ProtobufCMessage *msg)
 
 int collect_signalfd(void)
 {
-	return collect_image(CR_FD_SIGNALFD, PB_SIGNALFD,
+	int ret = collect_image(CR_FD_SIGNALFD, PB_SIGNALFD,
 			sizeof(struct signalfd_info), collect_one_sigfd);
+
+	if (ret < 0 && errno == ENOENT)
+		return 0;
+
+	return ret;
 }

sk-packet.c

@@ -497,6 +497,11 @@ static int collect_one_packet_sk(void *o, ProtobufCMessage *base)
 
 int collect_packet_sockets(void)
 {
-	return collect_image(CR_FD_PACKETSK, PB_PACKETSK,
+	int ret = collect_image(CR_FD_PACKETSK, PB_PACKETSK,
 			sizeof(struct packet_sock_info), collect_one_packet_sk);
+
+	if (ret < 0 && errno == ENOENT)
+		return 0;
+
+	return ret;
 }

tty.c

@@ -972,6 +972,8 @@ int collect_tty(void)
 	ret = collect_image(CR_FD_TTY_INFO, PB_TTY_INFO,
 			    sizeof(struct tty_info_entry),
 			    collect_one_tty_info_entry);
+	if (ret && errno == ENOENT)
+		return 0;
 	if (!ret)
 		ret = collect_image(CR_FD_TTY, PB_TTY,
 				sizeof(struct tty_info),