bitbake: toaster: replace map with list comprehensions

map returns map object in python 3. Replaced calls of
map to equivalent list comprehensions in the code which
requires lists.

[YOCTO #9584]

(Bitbake rev: d41eb6d6c061cb35ec1ecd899f856876f9077167)

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/toaster/orm/models.py

@@ -1183,7 +1183,7 @@ class LayerIndexLayerSource(LayerSource):
 
         # update branches; only those that we already have names listed in the
         # Releases table
-        whitelist_branch_names = map(lambda x: x.branch_name, Release.objects.all())
+        whitelist_branch_names = [rel.branch_name for rel in Release.objects.all()]
         if len(whitelist_branch_names) == 0:
             raise Exception("Failed to make list of branches to fetch")