x11-misc/bumblebee-3.2.1 still uses runscript instead of openrc-run. There is a newer (masked) version 3.2.1_p20170123 but I was unable to find the change log.
If you sync, and emerge bumblebee (any version) you'll have the init script with openrc-run. This was done without a revbump (as has been done with this fix for many other packages) because it isn't worth recompiling a package to experience this change. You certainly can recompile it if you want. Also, I should probably move to stabilize 3.2.1_p20170123... but that's a separate point. Feel free to reopen this bug if you still experience a problem after a sync and re-emerge.