Fix #34194: Render Layer node didn't initialize color management flag properly

Bang! How we didn't notice this for so long -- seems scenes came from render
layer node were rendering as if color management disabled (byte image wouldn't
be linearized).

git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@54460 954f8c5b-7b00-dc11-b283-0030488c597c