When using the VMware Paravirtualization SCSI controller type (where default is LSI Logic SAS), it causes the XenApp VDA to reboot after each update or deployment. This is becaus the driver gets installed every time when the MCS random machine boot up and prompt for a restart. Changing the SCSI Controller on the Master Image of VDA to LSI Logic SAS fixed the reboot issue.

Citrix is not responsible for and does not endorse or accept any responsibility for the contents or your use of these third party Web sites. Citrix is providing these links to you only as a convenience, and the inclusion of any link does not imply endorsement by Citrix of the linked Web site. It is your responsibility to take precautions to ensure that whatever Web site you use is free of viruses or other harmful items.

https://pubs.vmware.com/vsphere-51/index.jsp?topic=%2Fcom.vmware.vsphere.vm_admin.doc%2FGUID-0D73F44B-A586-41AD-B072-754548DEA1FE.html