I can confirm, what's worse is that Xen Server 7 will not boot if I have a mountpoint in /etc/fstab for my LV...due to same reason, LV being NOT AVAILABLE, halting systemd boot and downing my server. Seems like a bug...
Workaround for me was to set metadata_read_only to 0 in /etc/lvm.conf and add 'vgchange -a y' to /etc/rc.local like so
#!/bin/bash
# THIS FILE IS ADDED FOR COMPATIBILITY PURPOSES
#
# It is highly advisable to create own systemd services or udev rules
# to run scripts during boot instead of using this file.
#
# In contrast to previous versions due to parallel execution during boot
# this script will NOT be run after all other services.
#
# Please note that you must run 'chmod +x /etc/rc.d/rc.local' to ensure
# that this script will be executed during boot.
exec 2> /tmp/rc.local.log # send stderr from rc.local to a log file
exec 1>&2 # send stdout to the same log file
echo "rc.local started" # show start of execution
set -x # tell sh to display commands before execution
touch /var/lock/subsys/local
vgchange -a y
mount /dev/VG_XenStorage-0ddceea1-3812-d470-7b8a-85b7834adb19/ISO /mnt/iso
echo "rc.local completed"