Verbosely log the devstack run.

Add verbose logging for devstack to try and catch why the stack.sh
script may fail in some cases.

Change-Id: I1a0339923769451576730389e4bf127c01742afc

devstack-vm-gate-wrap.sh

@@ -180,6 +180,7 @@ function cleanup_host {
 
     sudo cp /var/log/syslog $WORKSPACE/logs/syslog.txt
     sudo cp $DEST/screen-logs/* $WORKSPACE/logs/
+    sudo cp $DEST/devstacklog.txt $WORKSPACE/logs/
 
     # Make the devstack localrc available with the logs
     sudo cp $DEST/devstack/localrc $WORKSPACE/logs/localrc.txt

devstack-vm-gate.sh

@@ -67,6 +67,8 @@ SKIP_EXERCISES=$SKIP_EXERCISES
 SERVICE_HOST=127.0.0.1
 SYSLOG=True
 SCREEN_LOGDIR=$DEST/screen-logs
+LOGFILE=$DEST/devstacklog.txt
+VERBOSE=True
 FIXED_RANGE=10.1.0.0/24
 FIXED_NETWORK_SIZE=256
 VIRT_DRIVER=$DEVSTACK_GATE_VIRT_DRIVER