We will depracate support of XenServer 6.5 since MOS10, this patch
is to implement this via:
(1) Add XCP version check in compute_pre_test.py to make sure
the minimal XCP version is 2.1.0
(2) Replace the guest tool to xe-guest-utilities_7.0.0-24_all.deb
(3) Update related documents to only support XS7.0 and XS7.1
Change-Id: I0a0420d158faf18de3534f501dd2a25d818cc9be