Wrong colorspace when same image used multiple times

[beatreichenbach]

I noticed a bug when using the same image multiple times with different color spaces and auto_tx is disabled.

To reproduce:

1. Create an image with color space "sRGB - Texture".
2. Create another image node pointing to the same file but using color space "Raw".
3. Disable auto_tx (for example when doing lookdev and not wanting to generate tx yet.)

The render will now use the "Raw" image for all instances of the image.