Add root mount point of container as irmap hint

Some packages monitor the FS /.

(00.573051) irmap: Scanning /. hint
(00.573053) irmap: Stat for 110025: INO - 2891453, DEV - 64768
(00.573055) irmap: Refresh stat for /.
(00.573063) irmap: MNTNS_ROOT: 110025, PATH: /., INO: 2891453, DEV: 64768
Signed-off-by: Nikolay Plotnik <nikolay.plotnik@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

irmap.c

@@ -57,6 +57,7 @@ static struct irmap hints[] = {
 	{ .path = "/etc", .nr_kids = -1, },
 	{ .path = "/var/spool", .nr_kids = -1, },
 	{ .path = "/lib/udev", .nr_kids = -1, },
+	{ .path = "/.", .nr_kids = 0, },
 	{ .path = "/no-such-path", .nr_kids = -1, },
 	{ },
 };