Run devstack zookeeper on tmpfs

We've seen connection losses to zookeeper during functional testing on
some cloud regions. Move zookeepers data dir to tmpfs to avoid io to the
disk costs.

Change-Id: If45d5cd7a2b63dbe7f20e7ef528b65ba41af7117

devstack/plugin.sh

@@ -651,6 +651,14 @@ EOF
     mkdir -p $HOME/.cache/openstack/
 }
 
+function nodepool_zk_on_tmpfs {
+    local datadir
+    datadir=$(sed -n -e 's/^dataDir=//p' /etc/zookeeper/conf/zoo.cfg)
+    sudo service zookeeper stop
+    sudo mount -t tmpfs -o nodev,nosuid,size=500M none $datadir
+    sudo service zookeeper start
+}
+
 # Create configs
 # Setup custom flavor
 function configure_nodepool {
@@ -694,6 +702,9 @@ function start_nodepool {
     export STATSD_PORT=8125
     run_process statsd "/usr/bin/socat -u udp-recv:$STATSD_PORT -"
 
+    # Restart nodepool's zk on a tmpfs
+    nodepool_zk_on_tmpfs
+
     # Ensure our configuration is valid.
     $NODEPOOL_INSTALL/bin/nodepool -c $NODEPOOL_CONFIG config-validate