* [jvm-packages] add hostIp and python exec for rabit tracker (#7808)
* Fix training continuation with categorical model. (#7810)
* Make sure the task is initialized before construction of tree updater.
This is a quick fix meant to be backported to 1.6, for a full fix we should pass the model
param into tree updater by reference instead.
Co-authored-by: Bobby Wang <wbo4958@gmail.com>