Source lib/neutron in boot_from_volume.sh

Without lib/neutron, boot_from_volume.sh generates the following
error:

  + _ping_check_neutron private 10.11.12.5 30
  /devstack/functions: line 356: _ping_check_neutron: command not found

Change-Id: Ib72c3f24d614570d69bf5dda35cbaf5847b1d1b9
diff --git a/exercises/boot_from_volume.sh b/exercises/boot_from_volume.sh
index 7912046..f679669 100755
--- a/exercises/boot_from_volume.sh
+++ b/exercises/boot_from_volume.sh
@@ -32,6 +32,7 @@
 
 # Import project functions
 source $TOP_DIR/lib/cinder
+source $TOP_DIR/lib/neutron
 
 # Import configuration
 source $TOP_DIR/openrc