Remove unnecessary call to fetch info_cache

The _heal_instance_info cache() always accesses instance['info_cache']
therefore we should always load the info_cache so we can avoid the extra
query to fetch it.

Change-Id: I3c2e005b98abf2a80276562cc05e88ba5ff199bc
Closes-bug: #1309239
Merge "Remove unnecessary call to fetch info_cache"