CLOUDSTACK-6437:
Add ability to distinguish between user defined and system defined guest OS and mappings
Add default mappings for XenServer

Local testing with
1. Add new guest OS by API
2. Add new guest OS mapping by API
Review from pyr https://reviews.apache.org/r/20557/
In 4.3, SSL was turned off by default.
However, for SSVM, the value from configuration server overrides the default in Config.java. Work around is to change in global properties.

Local testing, checking a fresh install has the above property false by default.

Signed-off-by: Nitin Mehta<nitin.mehta@citrix.com>
Fix log messages for vgpu creation.