Don't create BAT pack when rendering file in job storage directory

When the to-be-rendered blend file is contained in the job storage
directory, it is now assumed that all files are already reachable by the
Flamenco Workers. This supports environments working directly on shared
storage.

This assumes that the paths are already correct for the Flamenco
Workers. No detection of missing files is done (as BAT doesn't run).

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Blender Cloud changelog
 
+## Version 1.15 (in development)
+
+- Avoid creating BAT pack when the to-be-rendered file is already inside the job storage
+  directory. This assumes that the paths are already correct for the Flamenco Workers.
+
+
 ## Version 1.14 (2019-10-10)
 
 - Upgraded BAT to 1.2 for missing smoke caches, compatibility with Blender 2.81, and some