resources: virt: Allow hotplugging

This allows hot (un)plugging of CPU's! It also includes some general
cleanups which were necessary to support this as well as some other
features to the virt resource. Hotunplug requires Fedora 25.

It also comes with a mini shell script to help demo this capability.

Many thanks to pkrempa for his help with the libvirt API!

misc/delta-cpu.sh

@@ -0,0 +1,81 @@
+#!/bin/bash
+# shitty cpu count control, useful for live demos
+
+minimum=1	# don't decrease below this number of cpus
+maximum=8	# don't increase above this number of cpus
+count=1		# initial count
+factor=3
+function output() {
+count=$1	# arg!
+cat << EOF > ~/code/mgmt/examples/virt4.yaml
+---
+graph: mygraph
+resources:
+  virt:
+  - name: mgmt4
+    meta:
+      limit: .inf
+      burst: 0
+    uri: 'qemu:///session'
+    cpus: $count
+    maxcpus: $maximum
+    memory: 524288
+    boot:
+    - hd
+    disk:
+    - type: qcow2
+      source: "~/.local/share/libvirt/images/fedora-23-scratch.qcow2"
+    state: running
+    transient: false
+edges: []
+comment: "qemu-img create -b fedora-23.qcow2 -f qcow2 fedora-23-scratch.qcow2"
+EOF
+}
+#tput cuu 1 && tput el	# remove last line
+str=''
+tnuoc=$((maximum-count))	# backwards count
+count2=$((count * factor))
+tnuoc2=$((tnuoc * factor))
+left=`yes '>' | head -$count2 | paste -s -d '' -`
+right=`yes ' ' | head -$tnuoc2 | paste -s -d '' -`
+str="${left}${right}"
+_min=$((minimum-1))
+_max=$((maximum+1))
+reset	# clean up once...
+output $count	# call function
+while true; do
+
+	read -n1 -r -s -p "CPUs count is: $count; ${str} Press +/- key to adjust." key
+	if [ "$key" = "q" ] || [ "$key" = "Q" ]; then
+		echo	# newline
+		exit
+	fi
+	if [ ! "$key" = "+" ] && [ ! "$key" = "-" ] && [ ! "$key" = "=" ] && [ ! "$key" = "_" ]; then	# wrong key
+		reset	# woops, reset it all...
+		continue
+	fi
+	if [ "$key" == "+" ] || [ "$key" == "=" ]; then
+		count=$((count+1))
+	fi
+	if [ "$key" == "-" ] || [ "$key" == "_" ]; then
+		count=$((count-1))
+	fi
+	if [ $count -eq $_min ]; then	# min
+		count=$minimum
+	fi
+	if [ $count -eq $_max ]; then	# max
+		count=$maximum
+	fi
+
+	tnuoc=$((maximum-count))	# backwards count
+	#echo "count is: $count"
+	#echo "tnuoc is: $tnuoc"
+	count2=$((count * factor))
+	tnuoc2=$((tnuoc * factor))
+	left=`yes '>' | head -$count2 | paste -s -d '' -`
+	right=`yes ' ' | head -$tnuoc2 | paste -s -d '' -`
+	str="${left}${right}"
+	#echo "str is: $str"
+	echo -ne '\r'	# backup
+	output $count	# call function
+done