Remove dependency on pkg/brokerapi

[pmorie]

Remove the only dependency we have in production code on this package.

[duglin]

Why would it not be better to let the brokerapi define this constant since if it changes in the future it would be nice to have it happen automagically for us since its really the brokerapi layer that knows what value to put in there no? Or at least the default value. I can see us allowing people to override it though.

[pmorie]

@duglin the pkg/brokerapi package needs to go away from our production code - this is literally the only use of it. I'm fine pushing the constant into go-open-service-broker-api if that's more to your liking, but I want to eliminate the dependency on this package so we can move it out of pkg/ and into contrib/

WDYT

[MHBauer]

Current dependency is sort of a fake 'remote' dependency. Would prefer if we delegated to go-open-service-broker-api and the constant was defined there (along with other supported constants).

[MHBauer]

lint failure

Found 1 lint suggestions; failing.
pkg/controller/controller.go:57:2: exported const ContextProfilePlatformKubernetes should have comment (or a comment on this block) or be unexported

[MHBauer]

Should be fine as is. Made upstream issue kubernetes-retired/go-open-service-broker-client#79 to track.