virsh: add wrapper to serialize calls to virsh list

avoid storm of virsh list that overloads libvirtd API causing
unnecessary timeouts during pcmk monitoring operations.

Resolves: https://github.com/ClusterLabs/anvil/issues/395

Signed-off-by: Fabio M. Di Nitto <fabbione@fabbione.net>

Anvil/Tools.pm

@@ -1308,7 +1308,7 @@ sub _set_paths
 				useradd				=>	"/usr/sbin/useradd",
 				usermod				=>	"/usr/sbin/usermod",
 				uuidgen				=>	"/usr/bin/uuidgen",
-				virsh				=>	"/usr/bin/virsh",
+				virsh				=>	"/usr/sbin/anvil-virsh-wrapper",
 				'virt-install'			=>	"/usr/bin/virt-install",
 				websockify			=>	"/usr/bin/websockify",
 				wipefs				=>	"/usr/sbin/wipefs", 

tools/Makefile.am

@@ -1,7 +1,5 @@
 MAINTAINERCLEANFILES	= Makefile.in
 
-# XXX recheck after rebase!
-
 dist_sbin_SCRIPTS	= \
 			  anvil-access-module \
 			  anvil-boot-server \
@@ -46,6 +44,7 @@ dist_sbin_SCRIPTS	= \
 			  anvil-update-states \
 			  anvil-update-system \
 			  anvil-version-changes \
+			  anvil-virsh-wrapper \
 			  anvil-watch-bonds \
 			  anvil-watch-drbd \
 			  anvil-watch-power \

tools/anvil-virsh-wrapper

@@ -0,0 +1,10 @@
+#!/bin/sh -e
+
+(
+	if [ "$1" != "list" ]; then
+		virsh $@
+		exit $?
+	fi
+	flock -e 200
+	virsh $@
+) 200>/tmp/virsh.lock