cookbook/container: remove unexplained "exec >&2" lines.

These are often a good idea, but not necessary here and are distracting
to the tutorial, so let's just take them out.

Reported-by: Jeff Stearns <jeff.stearns@gmail.com>

docs/cookbook/container/default.runkvm.do

@@ -1,4 +1,3 @@
-exec >&2
 ./need.sh python kvm busybox
 
 redo-ifchange "$2.initrd" memcalc.py
@@ -7,7 +6,7 @@ rm -f "$3.out" "$3.code"
 # Linux only allows an initrd of size < 50% of RAM,
 # so set a RAM amount based on the initrd size.
 mem=$(./memcalc.py "$2.initrd")
-echo "$2: kvm memory required: $mem"
+echo "$2: kvm memory required: $mem" >&2
 
 kvm \
 	-m "$mem" \
@@ -21,7 +20,7 @@ kvm \
 	-chardev file,id=char2,path="$3.code" \
 	-serial chardev:char0 \
 	-serial chardev:char1 \
-	-serial chardev:char2
+	-serial chardev:char2 >&2
 read rv <$3.code || true
 [ -z "$rv" ] && exit 99
 if [ "$rv" -eq 0 ]; then