Destroy the bhyve vm after exit.

ansible/roles/bhyve/files/bhyve_netgraph_bridge.bash

@@ -52,7 +52,9 @@ function start_vm {
              # -s 29,fbuf,tcp=0.0.0.0:5900,w=1920,h=1080,wait \
     while true; do
         set -x
+        set +e
         bhyve \
+            -D \
             -c $CPU_CORES \
             -m $MEMORY \
             -H \
@@ -65,6 +67,7 @@ function start_vm {
             -l "bootrom,/usr/local/share/uefi-firmware/BHYVE_UEFI.fd,${mount_path}/BHYVE_UEFI_VARS.fd" \
             "$name"
         exit_code=$?
+        set -e
         set +x
         if [ $exit_code -eq 0 ]; then
             echo "Rebooting."
@@ -82,6 +85,9 @@ function start_vm {
             break
         fi
     done
+
+    bhyvectl "--vm=$name" --destroy
+    echo "Destroyed bhyve vm."
 }
 
 function detect_available_link {