CP-9798: Don't start a daemon from a udev RUN rule

udev on CentOS 7 kills all processes started from a RUN rule after it
finishes so don't start cdrommon from local-device-change because it
is called from a udev rule.

Instead, an instantiated systemd cdrommon service is started from the udev
rule.

Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>

scripts/local-device-change

@@ -24,8 +24,6 @@ DEVICE=$1 # foo
 
 /usr/bin/logger "local-device-change DEVICE=$DEVICE ACTION=$ACTION"
 
-CDROMMON="/opt/xensource/libexec/cdrommon"
-
 . /etc/xensource-inventory
 
 function remove_vdi {
@@ -45,7 +43,6 @@ do
     grep -q "^drive name:[	]*\W${DEVICE}\(\W\|$\)" /proc/sys/dev/cdrom/info
     # is this a CD or not
     if [ $? -eq 0 ]; then
-      ${CDROMMON} /dev/xapi/cd/${DEVICE}
       for SR in `xe sr-list type=udev sm-config:type=cd uuid=${LOCAL_SR} params=uuid --minimal`
       do
         xe vdi-introduce uuid=`uuidgen` sr-uuid=${SR} type=user location=/dev/xapi/cd/${DEVICE}