https://bugzilla.kernel.org/show_bug.cgi?id=116101
--- Comment #3 from Joe P. MonopolyMan720@aol.com --- (In reply to Christian König from comment #1)
Well as the error message already suggests "Userspace still has active objects !" you have an application which is still using the hardware.
So unbinding and rebinding it to the isn't possible in this state.
Just to show that it's working
$ glxinfo | grep "OpenGL renderer" OpenGL renderer string: Mesa DRI Intel(R) Sandybridge Server
$ DRI_PRIME=1 glxinfo | grep "OpenGL renderer" OpenGL renderer string: Gallium 0.4 on AMD HAWAII (DRM 2.43.0, LLVM 3.7.1)