Postpone color mode change until after boot animation

sRGB is only set by SurfaceFlinger when the default display is
wide color capable. Since we compute the best color mode on
every frame anyway for wide color capable displays, we can
simply move the sRGB set to the end of the boot animation.

Bug: 63823274
Test: Manual
Change-Id: I11bb6095acb63e66bcf7dff9e3f7b36588e371c1