[Differential] [Updated] D1711: Changes to the callout code to restore active semantics and also add a test-framework and test to validate thecallout code (and potentially for use by other tests).

[rrs (Randall Stewart)]

rrs added reviewers: jhb, kostikbel.

REVISION DETAIL
  https://reviews.freebsd.org/D1711

To: rrs, gnn, rwatson, sbruno, lstewart, imp, hselasky, adrian, jhb, kostikbel
Cc: jhb, kostikbel, emaste, delphij, neel, erj, freebsd-net