Add Instance.info_cache

This adds our first nested object: the InstanceInfoCache at
Instance.info_cache.

Related to blueprint unified-object-model

Change-Id: I2dd8727bbe38eadd080e9ea1ef9feabc2fa50520
Use InstanceList object for init_host

Related to blueprint unified-object-model

Change-Id: Idcc4da2a6807a58966e267c62a7f134ce58c890a
Merge "Add Instance.info_cache"
Merge "Use InstanceList object for init_host"
Merge remote-tracking branch 'm_src_repo/citrix-fixes' into build-temp